| 1. |
- Amundsen, Morten, et al.
(författare)
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Grain-boundary topological superconductor
- 2023
-
Ingår i: Communications Physics. - : Springer Nature. - 2399-3650. ; 6:1
-
Tidskriftsartikel (refereegranskat)abstract
- Majorana zero modes (MZMs) are of central importance for modern condensed matter physics and quantum information due to their non-Abelian nature, which thereby offers the possibility of realizing topological quantum bits. We here show that a grain boundary (GB) defect can host a topological superconductor (SC), with a pair of cohabitating MZMs at its end when immersed in a parent two-dimensional gapped topological SC with the Fermi surface enclosing a nonzero momentum. The essence of our proposal lies in the magnetic-field driven hybridization of the localized MZMs at the elementary blocks of the GB defect, the single lattice dislocations, due to the MZM spin being locked to the Burgers vector. Indeed, as we show through numerical and analytical calculations, the GB topological SC with two localized MZMs emerges in a finite range of both the angle and magnitude of the external magnetic field. Our work demonstrates the possibility of defect-based platforms for quantum information technology and opens up a route for their systematic search in future.
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| 2. |
- Argillander, Joakim, et al.
(författare)
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Quantum random number generation based on a perovskite light emitting diode
- 2023
-
Ingår i: Communications Physics. - : NATURE PORTFOLIO. - 2399-3650. ; 6:1
-
Tidskriftsartikel (refereegranskat)abstract
- True random number generation is not thought to be possible using a classical approach but by instead exploiting quantum mechanics genuine randomness can be achieved. Here, the authors demonstrate a certified quantum random number generation using a metal-halide perovskite light emitting diode as a source of weak coherent polarisation states randomly producing an output of either 0 or 1. The recent development of perovskite light emitting diodes (PeLEDs) has the potential to revolutionize the fields of optical communication and lighting devices, due to their simplicity of fabrication and outstanding optical properties. Here we demonstrate that PeLEDs can also be used in the field of quantum technologies by implementing a highly-secure quantum random number generator (QRNG). Modern QRNGs that certify their privacy are posed to replace classical random number generators in applications such as encryption and gambling, and therefore need to be cheap, fast and with integration capabilities. Using a compact metal-halide PeLED source, we generate random numbers, which are certified to be secure against an eavesdropper, following the quantum measurement-device-independent scenario. The obtained generation rate of more than 10 Mbit s(-1), which is already comparable to commercial devices, shows that PeLEDs can work as high-quality light sources for quantum information tasks, thus opening up future applications in quantum technologies.
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| 3. |
- Bárdfalvy, Dóra, et al.
(författare)
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Collective motion in a sheet of microswimmers
- 2024
-
Ingår i: Communications Physics. - 2399-3650. ; 7:1
-
Tidskriftsartikel (refereegranskat)abstract
- Self-propelled particles such as bacteria or algae swimming through a fluid are non-equilibrium systems where particle motility breaks microscopic detailed balance, often resulting in large-scale collective motion. Previous theoretical work has identified long-ranged hydrodynamic interactions as the driver of collective motion in unbounded suspensions of rear-actuated (“pusher”) microswimmers. In contrast, most experimental studies of collective motion in microswimmer suspensions have been carried out in restricted geometries where both the swimmers’ motion and their long-range flow fields become altered due to the proximity of a boundary. Here, we study numerically a minimal model of microswimmers in such a restricted geometry, where the particles move in the midplane between two no-slip walls. For pushers, we demonstrate collective motion with short-ranged order, in contrast with the long-ranged flows observed in unbounded systems. For front-actuated (“puller”) microswimmers, we discover a long-wavelength density instability resulting in the formation of dense microswimmer clusters. Both types of collective motion are fundamentally different from their previously studied counterparts in unbounded domains. Our results show that this difference is dictated by the geometrical restriction of the swimmers’ motion, while hydrodynamic screening due to the presence of a wall is subdominant in determining the suspension’s collective state.
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| 4. |
- Blomquist, Emil, et al.
(författare)
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Unbiased description of magnetic polarons in a Mott insulator
- 2020
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Ingår i: Communications Physics. - : Springer Nature. - 2399-3650. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Polarons are elementary quasi-particles characterizing several interacting many-body quantum systems. The authors present an unbiased Quantum Monte Carlo simulation of a magnetic polaron in a t-J model at low-temperature, and find excellent agreement with a recent experimental realization in the framework of cold-atoms systems. Polarons are among the most elementary quasiparticles of interacting quantum matter, consisting of a charge carrier dressed by an excited background. In Mott insulators, they take the form of a dopant surrounded by a distorted spin-background. Despite the fundamental importance of polarons for the electronic structure of strongly correlated systems, access to their internal structure was only recently realized in experiments, while controllable theoretical results are still lacking due to the sign problem. Here we report unbiased high-precision data obtained from worm-algorithm Monte Carlo that reveal the real-space structure of a polaron in thet-Jmodel deep inside the region where the sign problem becomes significant. These results are directly comparable to recent quantum gas microscopy experiments, but give access to significantly lower temperatures.
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| 5. |
- Choudhary, Akash, et al.
(författare)
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Orientational dynamics and rheology of active suspensions in weakly viscoelastic flows
- 2023
-
Ingår i: Communications Physics. - : Springer Nature. - 2399-3650. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- Microswimmers in a fluid are an example of an active suspension whereby the system is driven out of equilibrium though the interaction of the microswimmers with their surrounding environment. Here, the authors study the orientational microstructure of active suspensions in a viscoelastic fluid and show how the activity of the microswimmers can alter the bulk properties. Microswimmer suspensions in Newtonian fluids exhibit unusual macroscale properties, such as a superfluidic behavior, which can be harnessed to perform work at microscopic scales. Since most biological fluids are non-Newtonian, here we study the rheology of a microswimmer suspension in a weakly viscoelastic shear flow. At the individual level, we find that the viscoelastic stresses generated by activity substantially modify the Jeffery orbits well-known from Newtonian fluids. The orientational dynamics depends on the swimmer type; especially pushers can resist flow-induced rotation and align at an angle with the flow. To analyze its impact on bulk rheology, we study a dilute microswimmer suspension in the presence of random tumbling and rotational diffusion. Strikingly, swimmer activity and its elastic response in polymeric fluids alter the orientational distribution and substantially amplify the swimmer-induced viscosity. This suggests that pusher suspensions reach the superfluidic regime at lower volume fractions compared to a Newtonian fluid with identical viscosity.
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| 6. |
- Crialesi-Esposito, Marco, et al.
(författare)
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The interaction of droplet dynamics and turbulence cascade
- 2023
-
Ingår i: Communications Physics. - : Springer Nature. - 2399-3650. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- The dynamics of droplet fragmentation in turbulence is described by the Kolmogorov-Hinze framework. Yet, a quantitative theory is lacking at higher concentrations when strong interactions between the phases and coalescence become relevant, which is common in most flows. Here, we address this issue through a fully-coupled numerical study of the droplet dynamics in a turbulent flow at R-lambda & AP; 140, the highest attained up to now. By means of time-space spectral statistics, not currently accessible to experiments, we demonstrate that the characteristic scale of the process, the Hinze scale, can be precisely identified as the scale at which the net energy exchange due to capillarity is zero. Droplets larger than this scale preferentially break up absorbing energy from the flow; smaller droplets, instead, undergo rapid oscillations and tend to coalesce releasing energy to the flow. Further, we link the droplet-size distribution with the probability distribution of the turbulent dissipation. This shows that key in the fragmentation process is the local flux of energy which dominates the process at large scales, vindicating its locality.
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| 7. |
- Deca, Jan, et al.
(författare)
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Reiner Gamma albedo features reproduced by modeling solar wind standoff
- 2018
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Ingår i: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 1
-
Tidskriftsartikel (refereegranskat)abstract
- All lunar swirls are known to be co-located with crustal magnetic anomalies (LMAs). Not all LMAs can be associated with albedo markings, making swirls, and their possible connection with the former, an intriguing puzzle yet to be solved. By coupling fully kinetic simulations with a Surface Vector Mapping model, we show that solar wind standoff, an ion–electron kinetic interaction mechanism that locally prevents weathering by solar wind ions, reproduces the shape of the Reiner Gamma albedo pattern. Our method reveals why not every magnetic anomaly forms a distinct albedo marking. A qualitative match between optical remote observations and in situ particle measurements of the back-scattered ions is simultaneously achieved, demonstrating the importance of a kinetic approach to describe the solar wind interaction with LMAs. The anti-correlation between the predicted amount of surface weathering and the surface reflectance is strongest when evaluating the proton energy flux.
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| 8. |
- Dong, Xiao Xia, et al.
(författare)
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Carrier-envelope-phase measurement of sub-cycle UV pulses using angular photofragment distributions
- 2022
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Ingår i: Communications Physics. - : Springer Nature. - 2399-3650. ; 5:1
-
Tidskriftsartikel (refereegranskat)abstract
- Carrier-envelope-phase (CEP) of sub-cycle ultraviolet (UV) pulse strongly influences the dynamics of quantum systems, but its characterization is not accessible experimentally. Here we investigate photodissociation of a diatomic molecule from its ground-rovibrational state in a linearly polarized weak sub-cycle UV pulse with a controlled CEP. The angular distribution of photofragments shows an asymmetric profile deviating from the well-known cos(2-) or sin(2)-like ones, which can be identified as a way to imprint CEP. We unveil that such an effect stems from the temporal neighboring rotational excitation by molecular permanent dipole interaction through the joint contributions between counter-rotating and rotating terms. This in turn, opens different pathways in photodissociation dynamics. Given that the temporal excitation between various states with close energies can be manipulated by CEP of subcycle UV pulses, our results pave ways for understanding and manipulating electron, nuclear and their joint dynamics with variation of CEP of attosecond pulses.
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| 9. |
- Eriksson, Anton, et al.
(författare)
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How choosing random-walk model and network representation matters for flow-based community detection in hypergraphs
- 2021
-
Ingår i: Communications Physics. - : Nature Publishing Group. - 2399-3650. ; 4:1
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Tidskriftsartikel (refereegranskat)abstract
- Hypergraphs offer an explicit formalism to describe multibody interactions in complex systems. To connect dynamics and function in systems with these higher-order interactions, network scientists have generalised random-walk models to hypergraphs and studied the multibody effects on flow-based centrality measures. Mapping the large-scale structure of those flows requires effective community detection methods applied to cogent network representations. For different hypergraph data and research questions, which combination of random-walk model and network representation is best? We define unipartite, bipartite, and multilayer network representations of hypergraph flows and explore how they and the underlying random-walk model change the number, size, depth, and overlap of identified multilevel communities. These results help researchers choose the appropriate modelling approach when mapping flows on hypergraphs.
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| 10. |
- Ferri, Julien, 1990, et al.
(författare)
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Enhanced target normal sheath acceleration using colliding laser pulses
- 2019
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Ingår i: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 2
-
Tidskriftsartikel (refereegranskat)abstract
- Laser-solid interaction can lead to the acceleration of protons to tens of MeV. Here, we show that a strong enhancement of this acceleration can be achieved by splitting the laser pulse to two parts of equal energy and opposite incidence angles. Through the use of two- and three-dimensional Particle-In-Cell simulations, we find that the multi-pulse interaction leads to a standing wave pattern at the front side of the target, with an enhanced electric field and a substantial modification of the hot electron generation process. This in turn leads to significant improvement of the proton spectra, with an almost doubling of the accelerated proton energy and five-fold enhancement of the number of protons. The proposed scheme is robust with respect to incidence angles for the laser pulses, providing flexibility to the scheme, which should facilitate its experimental implementation.
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| 11. |
- Fonseca, Nelson J. G., et al.
(författare)
-
A solution to the complement of the generalized Luneburg lens problem
- 2021
-
Ingår i: Communications Physics. - : Springer Nature. - 2399-3650. ; 4:1
-
Tidskriftsartikel (refereegranskat)abstract
- Lenses are of interest for the design of directive antennas and multi-optics instruments in the microwave, terahertz and optical domains. Here, we introduce an optical problem defined as the complement of the well-known generalized Luneburg lens problem. The spherically symmetric inhomogeneous lenses obtained as solutions of this problem transform a given sphere in the homogeneous region outside of the lens into a virtual conjugate sphere, forming a virtual image from a real source. An analytical solution is proposed for the equivalent geodesic lens using the analogy between classical mechanics and geometrical optics. The refractive index profile of the corresponding inhomogeneous lens is then obtained using transformation optics. The focusing properties of this family of lenses are validated using ray-tracing models, further corroborated with full-wave simulations. The numerical results agree well with the predictions over the analyzed frequency bandwidth (10-30 GHz). This virtual focusing property may further benefit from recent developments in the fields of metamaterials and transformation optics. Spherically-symmetric lenses can create sharp virtual images, but a general expression for their refractive index profiles had not yet been developed. Here, this expression is provided via analogy between classical mechanics and geometrical optics, yielding solutions complementary to existing lenses obtained from the generalized Luneburg lens problem.
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| 12. |
- Fransson, Erik, 1990, et al.
(författare)
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Limits of the phonon quasi-particle picture at the cubic-to-tetragonal phase transition in halide perovskites
- 2023
-
Ingår i: Communications Physics. - 2399-3650. ; 6:1
-
Tidskriftsartikel (refereegranskat)abstract
- The soft modes associated with continuous-order phase transitions are associated with strong anharmonicity. This leads to the overdamped limit where the phonon quasi-particle picture can break down. However, this limit is commonly restricted to a narrow temperature range, making it difficult to observe its signature feature, namely the breakdown of the inverse relationship between the relaxation time and damping. Here we present a physically intuitive picture based on the relaxation times of the mode coordinate and its conjugate momentum, which at the instability approach infinity and the inverse damping factor, respectively. We demonstrate this behavior for the cubic-to-tetragonal phase transition of the inorganic halide perovskite CsPbBr3 via molecular dynamics simulations, and show that the overdamped region extends almost 200 K above the transition temperature. Further, we investigate how the dynamics of these soft phonon modes change when crossing the phase transition.
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| 13. |
- Ge, Yuqing, 1996, et al.
(författare)
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Constructing coarse-grained skyrmion potentials from experimental data with Iterative Boltzmann Inversion
- 2023
-
Ingår i: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 6:1
-
Tidskriftsartikel (refereegranskat)abstract
- In an effort to understand skyrmion behavior on a coarse-grained level, skyrmions are often described as 2D quasiparticles evolving according to the Thiele equation. Interaction potentials are the key missing parameters for predictive modeling of experiments. Here, the Iterative Boltzmann Inversion technique commonly used in soft matter simulations is applied to construct potentials for skyrmion-skyrmion and skyrmion-magnetic material boundary interactions from a single experimental measurement without any prior assumptions of the potential form. It is found that the two interactions are purely repulsive and can be described by an exponential function for micrometer-sized skyrmions in a ferromagnetic thin film multilayer stack. This captures the physics on experimental length and time scales that are of interest for most skyrmion applications and typically inaccessible to atomistic or micromagnetic simulations.
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| 14. |
- Giunta, Giovanni, et al.
(författare)
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Optimal spatial allocation of enzymes as an investment problem
- 2022
-
Ingår i: Communications Physics. - : Springer Nature. - 2399-3650. ; 5:1
-
Tidskriftsartikel (refereegranskat)abstract
- Cells face various allocation problems demanding decisions on how to distribute their finite resources. They decide which enzymes to produce at what quantity, but also where to position them. Here we focus on the spatial allocation problem of arranging enzymes such as to maximize the total reaction flux produced by them in a system with given geometry and boundary conditions. We derive an optimal allocation principle demanding that the available enzymes are distributed such that the marginal flux returns at each occupied position are equal. This 'homogeneous marginal returns' (HMR) criterion corresponds to a portfolio optimization of investments that globally feed back onto all payoffs. The HMR criterion allows us to analytically understand and characterize a localization-delocalization transition in the optimal enzyme distribution. Our analysis reveals the generality of the transition, and produces a practical test for the optimality of enzyme clustering by comparing the reaction flux to the influx of substrate. Based on these results, we devise an additive construction scheme, which builds up optimal enzyme arrangements systematically rather than by trial and error. Taken together, we identify a common principle in allocation problems from biology and economics, which also serves as a design principle for synthetic biomolecular systems.
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| 15. |
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| 16. |
- Hansson, Tobias, et al.
(författare)
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Modeling of dual frequency combs and bistable solitons in third-harmonic generation
- 2023
-
Ingår i: Communications Physics. - : NATURE PORTFOLIO. - 2399-3650. ; 6:1
-
Tidskriftsartikel (refereegranskat)abstract
- Third-harmonic generation frequency combs grant telecom pump laser sources the direct and simultaneous access to both the near infrared and the visible spectral regions. The authors model the broadband and temporally dispersive dual-comb generation, and identify conditions for accessing a regime supporting two distinct and coexisting cavity solitons. Phase-matching of the third-harmonic generation process can be used to extend the emission of radiation from Kerr microresonators into new spectral regions far from the pump wavelength. Here, we present a theoretical mean-field model for optical frequency combs in a dissipative and nonlinear chi((3))-based cavity system with parametric coupling between fundamental and third-harmonic waves. We investigate temporally dispersive dual-comb generation of phase-matched combs with broad bandwidth and anomalous dispersion of the fundamental field, individuating conditions for accessing a multistable regime that simultaneously supports two types of coupled bright cavity solitons. These bistable cavity solitons coexist for the same pump power and frequency detuning, while featuring dissimilar amplitudes of their individual field components. Third-harmonic generation frequency combs grant telecom pump laser sources a simultaneous and direct access to both the near-infrared and the visible regions, which may prove advantageous for the development of optical clocks and sensing applications.
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| 17. |
- He, Yuchi, et al.
(författare)
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Charge density waves and their transitions in anisotropic quantum Hall systems
- 2021
-
Ingår i: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 4:1
-
Tidskriftsartikel (refereegranskat)abstract
- In recent experiments, external anisotropy has been a useful tool to tune different phases and study their competitions. In this paper, we look at the quantum Hall charge density wave states in the N=2 Landau level. Without anisotropy, there are two first-order phase transitions between the Wigner crystal, the 2-electron bubble phase, and the stripe phase. By adding mass anisotropy, our analytical and numerical studies show that the 2-electron bubble phase disappears and the stripe phase significantly enlarges its domain in the phase diagram. Meanwhile, a regime of stripe crystals that may be observed experimentally is unveiled after the bubble phase gets out. Upon increase of the anisotropy, the energy of the phases at the transitions becomes progressively smooth as a function of the filling. We conclude that all first-order phase transitions are replaced by continuous phase transitions, providing a possible realisation of continuous quantum crystalline phase transitions. The quantum Hall effect can be used to study the physics of correlated systems and can reveal different features of the associated phase transitions. Here, the authors consider mass anisotropy and the impact on the phase transitions of quantum Hall charge density wave states in a 2D electron gas.
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| 18. |
- He, Y. T., et al.
(författare)
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Dominance of gamma-gamma electron-positron pair creation in a plasma driven by high-intensity lasers
- 2021
-
Ingår i: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 4:1
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Tidskriftsartikel (refereegranskat)abstract
- Creation of electrons and positrons from light alone is a basic prediction of quantum electrodynamics, but yet to be observed. Our simulations show that the required conditions are achievable using a high-intensity two-beam laser facility and an advanced target design. Dual laser irradiation of a structured target produces high-density gamma rays that then create > 10(8) positrons at intensities of 2 x 10(22) Wcm(-2). The unique feature of this setup is that the pair creation is primarily driven by the linear Breit-Wheeler process (gamma gamma -> e(+)e(-)), which dominates over the nonlinear Breit-Wheeler and Bethe-Heitler processes. The favorable scaling with laser intensity of the linear process prompts reconsideration of its neglect in simulation studies and also permits positron jet formation at experimentally feasible intensities. Simulations show that the positrons, confined by a quasistatic plasma magnetic field, may be accelerated by the lasers to energies >200 MeV. Electron-positron pair generation from nonlinear quantum electrodynamics is predicted at high intensities that are, so far, beyond experimental capabilities. Here, simulations predict a high yield of positrons can be obtained from gamma-gamma photon collisions in the linear regime, using counter-propagating pulses and a microstructured target.
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| 19. |
- Hennecke, Martin, et al.
(författare)
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Ultrafast opto-magnetic effects in the extreme ultraviolet spectral range
- 2024
-
Ingår i: Communications Physics. - : Springer Nature. - 2399-3650. ; 7:1
-
Tidskriftsartikel (refereegranskat)abstract
- Coherent light-matter interactions mediated by opto-magnetic phenomena like the inverse Faraday effect (IFE) are expected to provide a non-thermal pathway for ultrafast manipulation of magnetism on timescales as short as the excitation pulse itself. As the IFE scales with the spin-orbit coupling strength of the involved electronic states, photo-exciting the strongly spin-orbit coupled core-level electrons in magnetic materials appears as an appealing method to transiently generate large opto-magnetic moments. Here, we investigate this scenario in a ferrimagnetic GdFeCo alloy by using intense and circularly polarized pulses of extreme ultraviolet radiation. Our results reveal ultrafast and strong helicity-dependent magnetic effects which are in line with the characteristic fingerprints of an IFE, corroborated by ab initio opto-magnetic IFE theory and atomistic spin dynamics simulations.
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| 20. |
- Higley, Daniel J., et al.
(författare)
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Stimulated resonant inelastic X-ray scattering in a solid
- 2022
-
Ingår i: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 5
-
Tidskriftsartikel (refereegranskat)abstract
- When materials are exposed to X-ray pulses with sufficiently high intensity, various nonlinear effects can occur. The most fundamental one consists of stimulated electronic decays after resonant absorption of X-rays. Such stimulated decays enhance the number of emitted photons and the emission direction is confined to that of the stimulating incident photons which clone themselves in the process. Here we report the observation of stimulated resonant elastic (REXS) and inelastic (RIXS) X-ray scattering near the cobalt L3 edge in solid Co/Pd multilayer samples. We observe an enhancement of order 106 of the stimulated over the conventional spontaneous RIXS signal into the small acceptance angle of the RIXS spectrometer. We also find that in solids both stimulated REXS and RIXS spectra contain contributions from inelastic electron scattering processes, even for ultrashort 5 fs pulses. Our results reveal the potential and caveats of the development of stimulated RIXS in condensed matter.
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| 21. |
- Hoque, Anamul Md, 1988, et al.
(författare)
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All-electrical creation and control of spin-galvanic signal in graphene and molybdenum ditelluride heterostructures at room temperature
- 2021
-
Ingår i: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 4:1
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Tidskriftsartikel (refereegranskat)abstract
- The ability to engineer new states of matter and control their spintronic properties by electric fields is at the heart of future information technology. Here, we report a gate-tunable spin-galvanic effect in van der Waals heterostructures of graphene with a semimetal of molybdenum ditelluride at room temperature due to an efficient spin-charge conversion process. Measurements in different device geometries with control over the spin orientations exhibit spin-switch and Hanle spin precession behavior, confirming the spin origin of the signal. The control experiments with the pristine graphene channels do not show any such signals. We explain the experimental spin-galvanic signals by theoretical calculations considering the spin-orbit induced spin-splitting in the bands of the graphene in the heterostructure. The calculations also reveal an unusual spin texture in graphene heterostructure with an anisotropic out-of-plane and in-plane spin polarization. These findings open opportunities to utilize graphene-based heterostructures for gate-controlled spintronic devices.
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| 22. |
- Horio, M., et al.
(författare)
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Orbital-selective metal skin induced by alkali-metal-dosing Mott-insulating Ca 2 RuO 4
- 2023
-
Ingår i: Communications Physics. - 2399-3650. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- Doped Mott insulators are the starting point for interesting physics such as high temperature superconductivity and quantum spin liquids. For multi-band Mott insulators, orbital selective ground states have been envisioned. However, orbital selective metals and Mott insulators have been difficult to realize experimentally. Here we demonstrate by photoemission spectroscopy how Ca2RuO4, upon alkali-metal surface doping, develops a single-band metal skin. Our dynamical mean field theory calculations reveal that homogeneous electron doping of Ca2RuO4 results in a multi-band metal. All together, our results provide evidence for an orbital-selective Mott insulator breakdown, which is unachievable via simple electron doping. Supported by a cluster model and cluster perturbation theory calculations, we demonstrate a type of skin metal-insulator transition induced by surface dopants that orbital-selectively hybridize with the bulk Mott state and in turn produce coherent in-gap states.
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| 23. |
- Hörnedal, Niklas, et al.
(författare)
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Ultimate speed limits to the growth of operator complexity
- 2022
-
Ingår i: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 5:1
-
Tidskriftsartikel (refereegranskat)abstract
- In an isolated system, the time evolution of a given observable in the Heisenberg picture can be efficiently represented in Krylov space. In this representation, an initial operator becomes increasingly complex as time goes by, a feature that can be quantified by the Krylov complexity. We introduce a fundamental and universal limit to the growth of the Krylov complexity by formulating a Robertson uncertainty relation, involving the Krylov complexity operator and the Liouvillian, as generator of time evolution. We further show the conditions for this bound to be saturated and illustrate its validity in paradigmatic models of quantum chaos.
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| 24. |
- Jünger, Christian, et al.
(författare)
-
Intermediate states in Andreev bound state fusion
- 2023
-
Ingår i: Communications Physics. - 2399-3650. ; 6:1
-
Tidskriftsartikel (refereegranskat)abstract
- Hybridization is one of the most fundamental quantum mechanical phenomena, with the text book example of binding two hydrogen atoms in a hydrogen molecule. Here we report tunnel spectroscopy experiments illustrating the hybridization of another type of discrete quantum states, namely of superconducting subgap states that form in segments of a semiconducting nanowire in contact with superconducting reservoirs. We discuss a collection of intermediate states with unique (tunnel) spectroscopic fingerprints in the process of merging well-known individual bound states, hybridized by a central quantum dot and eventually coherently linking the reservoirs, carrying a Josephson current. These coupled and fused Andreev bound states can be seen as superconducting analogues to atomic and molecular single electron states in nature, and explain a variety of recent bound state spectra, with specific fingerprints that will have to be winnowed in future Majorana fusion experiments.
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| 25. |
- Jünger, Christian, et al.
(författare)
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Spectroscopy of the superconducting proximity effect in nanowires using integrated quantum dots
- 2019
-
Ingår i: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 2:1
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Tidskriftsartikel (refereegranskat)abstract
- The superconducting proximity effect has recently attracted a renewed interest as the basis of topologically nontrivial states in materials with a large spin–orbit interaction, with protected boundary states useful for quantum information technologies. However, spectroscopy of these states is challenging because of the limited control of conventional tunnel barriers. Here we report electronic spectroscopy measurements of the proximity gap in a semiconducting indium arsenide nanowire segment coupled to a superconductor, using quantum dots formed deterministically during the crystal growth. We extract characteristic parameters describing the proximity gap, which is suppressed for lower electron densities and fully developed for larger ones. This gate-tunable transition of the proximity effect can be understood as a transition from the long to the short junction regime of subgap bound states in the NW segment. Our device architecture opens up the way to systematic, quantitative spectroscopy studies of subgap states, such as Majorana-bound states.
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| 26. |
- Juričić, Vladimir, et al.
(författare)
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Yukawa-Lorentz symmetry in non-Hermitian Dirac materials
- 2024
-
Ingår i: Communications Physics. - : Springer Nature. - 2399-3650. ; 7:1
-
Tidskriftsartikel (refereegranskat)abstract
- Lorentz space–time symmetry represents a unifying feature of the fundamental forces, typically manifest at sufficiently high energies, while in quantum materials it emerges in the deep low-energy regime. However, its fate in quantum materials coupled to an environment thus far remained unexplored. We here introduce a general framework of constructing symmetry-protected Lorentz-invariant non-Hermitian (NH) Dirac semimetals (DSMs), realized by invoking masslike anti-Hermitian Dirac operators to its Hermitian counterpart. Such NH DSMs feature purely real or imaginary isotropic linear band dispersion, yielding a vanishing density of states. Dynamic mass orderings in NH DSMs thus take place for strong Hubbard-like local interactions through a quantum phase transition, hosting a non-Fermi liquid, beyond which the system becomes an insulator. We show that depending on the internal Clifford algebra between the NH Dirac operator and candidate mass order-parameter, the resulting quantum-critical fluid either remains coupled with the environment or recovers full Hermiticity by decoupling from the bath, while always enjoying an emergent Yukawa-Lorentz symmetry in terms of a unique terminal velocity. We showcase the competition between such mass orderings, their hallmarks on quasi-particle spectra in the ordered phases, and the relevance of our findings for correlated designer NH Dirac materials.
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| 27. |
- K. Manikandan, Sreekanth, et al.
(författare)
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Quantitative analysis of non-equilibrium systems from short-time experimental data
- 2021
-
Ingår i: Communications Physics. - : Springer Nature. - 2399-3650. ; 4:1
-
Tidskriftsartikel (refereegranskat)abstract
- Estimating entropy production directly from experimental trajectories is of great current interest but often requires a large amount of data or knowledge of the underlying dynamics. In this paper, we propose a minimal strategy using the short-time Thermodynamic Uncertainty Relation (TUR) by means of which we can simultaneously and quantitatively infer the thermodynamic force field acting on the system and the (potentially exact) rate of entropy production from experimental short-time trajectory data. We benchmark this scheme first for an experimental study of a colloidal particle system where exact analytical results are known, prior to studying the case of a colloidal particle in a hydrodynamical flow field, where neither analytical nor numerical results are available. In the latter case, we build an effective model of the system based on our results. In both cases, we also demonstrate that our results match with those obtained from another recently introduced scheme. Thermal fluctuations play a crucial role in non-equilibrium phenomena at microscopic length scales, making it challenging to analyse and interpret experimental data. Here, the authors demonstrate that the short-time thermodynamic uncertainty relation inference scheme can estimate the entropy production rate for a colloidal particle in time-varying potentials and with background flows determined by the presence of a microbubble.
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| 28. |
- Katcko, K., et al.
(författare)
-
Spin-driven electrical power generation at room temperature
- 2019
-
Ingår i: Communications Physics. - : NATURE PUBLISHING GROUP. - 2399-3650. ; 2
-
Tidskriftsartikel (refereegranskat)abstract
- On-going research is exploring novel energy concepts ranging from classical to quantum thermodynamics. Ferromagnets carry substantial built-in energy due to ordered electron spins. Here, we propose to generate electrical power at room temperature by utilizing this magnetic energy to harvest thermal fluctuations on paramagnetic centers using spintronics. Our spin engine rectifies current fluctuations across the paramagnetic centers' spin states by utilizing so-called 'spinterfaces' with high spin polarization. Analytical and ab-initio theories suggest that experimental data at room temperature from a single MgO magnetic tunnel junction (MTJ) be linked to this spin engine. Device downscaling, other spintronic solutions to select a transport spin channel, and dual oxide/organic materials tracks to introduce paramagnetic centers into the tunnel barrier, widen opportunities for routine device reproduction. At present MgO MTJ densities in next-generation memories, this spin engine could lead to 'always-on' areal power densities that are highly competitive relative to other energy harvesting strategies.
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| 29. |
- Kirkley, Alec, et al.
(författare)
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Compressing network populations with modal networks reveal structural diversity
- 2023
-
Ingår i: Communications Physics. - : Springer Nature. - 2399-3650. ; 6:1
-
Tidskriftsartikel (refereegranskat)abstract
- Analyzing relational data consisting of multiple samples or layers involves critical challenges: How many networks are required to capture the variety of structures in the data? And what are the structures of these representative networks? We describe efficient nonparametric methods derived from the minimum description length principle to construct the network representations automatically. The methods input a population of networks or a multilayer network measured on a fixed set of nodes and output a small set of representative networks together with an assignment of each network sample or layer to one of the representative networks. We identify the representative networks and assign network samples to them with an efficient Monte Carlo scheme that minimizes our description length objective. For temporally ordered networks, we use a polynomial time dynamic programming approach that restricts the clusters of network layers to be temporally contiguous. These methods recover planted heterogeneity in synthetic network populations and identify essential structural heterogeneities in global trade and fossil record networks. Our methods are principled, scalable, parameter-free, and accommodate a wide range of data, providing a unified lens for exploratory analyses and preprocessing large sets of network samples.
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| 30. |
- Kuttruff, Joel, et al.
(författare)
-
Ultrafast all-optical switching enabled by epsilon-near-zero-tailored absorption in metal-insulator nanocavities
- 2020
-
Ingår i: Communications Physics. - : Nature Publishing Group. - 2399-3650. ; 3:1
-
Tidskriftsartikel (refereegranskat)abstract
- Ultrafast control of light−matter interactions is fundamental in view of new technological frontiers of information processing. However, conventional optical elements are either static or feature switching speeds that are extremely low with respect to the time scales at which it is possible to control light. Here, we exploit the artificial epsilon-near-zero (ENZ) modes of a metal-insulator-metal nanocavity to tailor the linear photon absorption of our system and realize a nondegenerate all-optical ultrafast modulation of the reflectance at a specific wavelength. Optical pumping of the system at its high energy ENZ mode leads to a strong redshift of the low energy mode because of the transient increase of the local dielectric function, which leads to a sub-3-ps control of the reflectance at a specific wavelength with a relative modulation depth approaching 120%.
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| 31. |
- Kuzmin, Leonid, 1946, et al.
(författare)
-
Photon-noise-limited cold-electron bolometer based on strong electron self-cooling for high-performance cosmology missions
- 2019
-
Ingår i: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 2:1
-
Tidskriftsartikel (refereegranskat)abstract
- Bolometers for balloon and space missions have seen extensive development because of their capacity to test primordial conditions of the Universe. The major improvements consist in lowering the operating temperature to reach higher sensitivities. Here we show that an array of 192 cold-electron bolometers (CEB) demonstrates photon-noise-limited operation at the cryostat temperature of 310 mK due to effective self-cooling of the absorber. The direct electron cooling of nanoabsorber placed between normal metal - insulator - superconductor junctions has considerably higher efficiency than indirect cooling through massive suspended platform, that requires overcoming a weak electron-phonon conductance. The electron temperature reached 120 mK without a power load, and 225 mK with a 60 pW power load with self-noise of a single bolometer below 3⋅10-18WHz-1∕2 at a 0.01 pW power load. This bolometer works at electron temperature less than phonon temperature, thus being a good candidate for future space missions without the use of dilution refrigerators.
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| 32. |
- Li, Hu, 1986-, et al.
(författare)
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Superior adhesion of graphene nanoscrolls
- 2018
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Ingår i: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 1
-
Tidskriftsartikel (refereegranskat)abstract
- An emerging material in the carbon family, a graphene nanoscroll (GNS) is composed of tubularly scrolled monolayer graphene and has shown superlubricity and large current sustainability, surpassing the properties of monolayer graphene itself. Here we report on the superior adhesion of GNS prepared with a high yield synthesis method that allows for mass production of high quality GNSs. Raman spectra indicate that the GNS still maintains the signature of monolayer graphene, implying the lacking of π-stacking between adjacent layers. Importantly, adhesion measurements using atomic force microscopy reveal these GNSs with height range of 120-130 nm show a 2.5-fold stronger adhesion force than pristine graphene. This result potentially indicates that the GNS has higher adhesion than monolayer graphene and even higher than the liquid-solid and hydrogen-bonding enhanced interfaces which are essential types of adhesions involved in the field of physical adhesions and thus, GNS could be a new candidate for super-strong and lightweight devices.
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| 33. |
- Litvinenko, Artem, 1989, et al.
(författare)
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A spinwave Ising machine
- 2023
-
Ingår i: Communications Physics. - 2399-3650. ; 6:1
-
Tidskriftsartikel (refereegranskat)abstract
- Time-multiplexed Coherent Ising Machines (CIMs) have demonstrated promising results in rapidly solving large-scale combinatorial problems. However, CIMs remain relatively large and power-demanding. Here, we demonstrate a spinwave-based Ising machine (SWIM) that due to the low spinwave group velocity allows for sufficient miniaturization and reduced power consumption. The SWIM is implemented using a 10-mm-long 5-mu m-thick Yttrium Iron Garnet film with off-the-shelf microwave components and can support an 8-spin MAX-CUT problem and solve it in less than 4 mu s consuming only 7 mu J. As the SWIM minimizes its energy, we observe that the spin states can demonstrate both uniform and domain-propagation-like switching. The developed SWIM has the potential for substantial further miniaturization with reduction of power consumption, scalability in the number of supported spins, increase of operational speed, and may become a versatile platform for commercially feasible high-performance solvers of combinatorial optimization problems.
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| 34. |
- Liu, Lei, et al.
(författare)
-
Pressure-induced magnetovolume effect in CoCrFeAl high-entropy alloy
- 2019
-
Ingår i: Communications Physics. - : NATURE PUBLISHING GROUP. - 2399-3650. ; 2
-
Tidskriftsartikel (refereegranskat)abstract
- High-entropy alloys (HEAs) composed of multiple-principal elements with (nearly) equimolar ratio establish a new conceptual framework for alloy design and hold a promise for extensive applications in industry, akin to the controlled expansion alloys (CEAs), such as Invar alloys. Spontaneously, one question emerges - would it be possible to synthesize a novel class of alloys combining the virtues of both CEAs and HEAs? Here, we report the pressure-induced magnetovolume effect in the body-centered-cubic CoCrFeAl HEA coupled with magnetic phase transitions from ferromagnetic to paramagnetic, and to non-magnetic states, originating from the successive collapses of local magnetic moments of Co and Fe. The observed magnetovolume anomalies, occurring in a progressive way, tailor appreciably the coefficient of thermal expansion of CoCrFeAl. These results further strengthen HEAs' anticipated potential for designing multifunctional materials in virtue of their multiple outstanding properties, and reveal possible routes for their future synthesis.
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| 35. |
- Löthman, Tomas, et al.
(författare)
-
Nematic superconductivity in magic-angle twisted bilayer graphene from atomistic modeling
- 2022
-
Ingår i: Communications Physics. - : Springer Nature. - 2399-3650. ; 5:1
-
Tidskriftsartikel (refereegranskat)abstract
- Twisted bilayer graphene (TBG) develops large moire patterns at small twist angles with flat energy bands hosting domes of superconductivity. The large system size and intricate band structure have however hampered investigations into the superconducting state. Here, using full-scale atomistic modelling with local electronic interactions, we find at and above experimentally relevant temperatures a highly inhomogeneous superconducting state with nematic ordering on both atomic and moire length scales. The nematic state has a locally anisotropic real-valued d-wave pairing, with a nematic vector winding throughout the moire pattern, and is three-fold degenerate. Although d-wave symmetric, the superconducting state has a full energy gap, which we tie to a pi-phase interlayer coupling. The superconducting nematicity is further directly detectable in the local density of states. Our results show that atomistic modeling is essential and also that very similar local interactions produce very different superconducting states in TBG and the high-temperature cuprate superconductors.
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| 36. |
- Mewes, L., et al.
(författare)
-
Energy relaxation pathways between light-matter states revealed by coherent two-dimensional spectroscopy
- 2020
-
Ingår i: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 3:1
-
Tidskriftsartikel (refereegranskat)abstract
- Coupling matter excitations to electromagnetic modes inside nano-scale optical resonators leads to the formation of hybrid light-matter states, so-called polaritons, allowing the controlled manipulation of material properties. Here, we investigate the photo-induced dynamics of a prototypical strongly-coupled molecular exciton-microcavity system using broadband two-dimensional Fourier transform spectroscopy and unravel the mechanistic details of its ultrafast photo-induced dynamics. We find evidence for a direct energy relaxation pathway from the upper to the lower polariton state that initially bypasses the excitonic manifold of states, which is often assumed to act as an intermediate energy reservoir, under certain experimental conditions. This observation provides new insight into polariton photophysics and could potentially aid the development of applications that rely on controlling the energy relaxation mechanism, such as in solar energy harvesting, manipulating chemical reactivity, the creation of Bose-Einstein condensates and quantum computing. Recent spectroscopic studies have elucidated light-matter interactions in exciton-polaritons at room temperature, yet their precise excited-state dynamics remain unclear. Here, broadband 2D Fourier transform spectroscopy reveals the relaxation between polaritonic states and the role of dark states.
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| 37. |
- Nulens, Lukas, et al.
(författare)
-
Catastrophic magnetic flux avalanches in NbTiN superconducting resonators
- 2023
-
Ingår i: Communications Physics. - 2399-3650. ; 6:1
-
Tidskriftsartikel (refereegranskat)abstract
- Macroscopic superconducting components are an important building block of various quantum circuits. Since several of the envisioned applications require exposure to magnetic fields, it is of utmost importance to explore the impact of magnetic fields on their performance. Here we explore the complex pattern of magnetic field penetration and identify its impact on the resonance frequency of NbTiN superconducting resonators by combining magneto-optical imaging and high-frequency measurements. At temperatures below approximately half of the superconducting critical temperature, the development of magnetic flux avalanches manifests itself as a noisy response in the field-dependent resonance frequency. Magneto-optical imaging reveals different regimes and distinguishes the impact of avalanches in the ground plane and resonator. Our findings demonstrate that superconducting resonators represent a valuable tool to investigate magnetic flux dynamics. Moreover, the current blooming of niobium-based superconducting radio-frequency devices makes this report timely by unveiling the severe implications of magnetic flux dynamics.
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| 38. |
- Ojala, Joonas, et al.
(författare)
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Reassigning the shapes of the 0+ states in the 186Pb nucleus
- 2022
-
Ingår i: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 5:1
-
Tidskriftsartikel (refereegranskat)abstract
- Across the physics disciplines, the 186Pb nucleus is the only known system, where the two first excited states, together with the ground state, form a triplet of zero-spin states assigned with prolate, oblate and spherical shapes. Here we report on a precision measurement where the properties of collective transitions in 186Pb were determined in a simultaneous in-beam γ-ray and electron spectroscopy experiment employing the recoil-decay tagging technique. The feeding of the 02+ state and the interband 22+→21+ transition have been observed. We also present direct measurement of the energies of the electric monopole transitions from the excited 0+ states to the 0+ ground state. In contrast to the earlier understanding, the obtained reduced transition probability B(E2;21+→02+) value of 190(80) W.u., the transitional quadrupole moment ∣Qt(21+→02+)∣=7.7(33) eb and intensity balance arguments provide evidence to reassign the 02+ and 03+ states with predominantly prolate and oblate shape, respectively. Our work demonstrates a step-up in experimental sensitivity and paves the way for systematic studies of electric monopole transitions in this region. These electric monopole transitions probe the nuclear volume in a unique manner and provide unexploited input for development of the next-generation energy density functional models.
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| 39. |
- Otsubo, Shun, et al.
(författare)
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Estimating time-dependent entropy production from non-equilibrium trajectories
- 2022
-
Ingår i: Communications Physics. - : Springer Nature. - 2399-3650. ; 5:1
-
Tidskriftsartikel (refereegranskat)abstract
- While methods for estimating the entropy production rate of a stationary process are relatively well established, this is still a challenge in non-stationary conditions. Here, the authors propose a scheme to infer the exact value of the time-dependent entropy production rate as well as entropy production along with single realizations directly from trajectory data. The rate of entropy production provides a useful quantitative measure of a non-equilibrium system and estimating it directly from time-series data from experiments is highly desirable. Several approaches have been considered for stationary dynamics, some of which are based on a variational characterization of the entropy production rate. However, the issue of obtaining it in the case of non-stationary dynamics remains largely unexplored. Here, we solve this open problem by demonstrating that the variational approaches can be generalized to give the exact value of the entropy production rate even for non-stationary dynamics. On the basis of this result, we develop an efficient algorithm that estimates the entropy production rate continuously in time by using machine learning techniques and validate our numerical estimates using analytically tractable Langevin models in experimentally relevant parameter regimes. Our method only requires time-series data for the system of interest without any prior knowledge of the system's parameters.
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| 40. |
- Ovesen, Simon, 1993, et al.
(författare)
-
Interlayer exciton dynamics in van der Waals heterostructures
- 2019
-
Ingår i: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 2:1
-
Tidskriftsartikel (refereegranskat)abstract
- Atomically thin transition metal dichalcogenides can be stacked to van der Waals heterostructures enabling the design of new materials with tailored properties. The strong Coulomb interaction gives rise to interlayer excitons, where electrons and holes are spatially separated in different layers. In this work, we reveal the time- and momentum-dependent elementary processes behind the formation, thermalization and photoemission of interlayer excitons for the exemplary MoSe2-WSe2 heterostructure. We identify tunneling of holes from MoSe2 to WSe2 on a ps timescale as the crucial process for interlayer exciton formation. We also predict a drastic reduction of the formation time as a function of the interlayer energy offset suggesting that interlayer excitons can be externally tuned. Finally, we explain the experimental observation of a dominant photoluminescence from interlayer excitons despite the vanishingly small oscillator strength as a consequence of huge interlayer exciton occupations at low temperatures.
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| 41. |
- Panigrahi, Archisman, et al.
(författare)
-
Projected topological branes
- 2022
-
Ingår i: Communications Physics. - : Springer Nature. - 2399-3650. ; 5:1
-
Tidskriftsartikel (refereegranskat)abstract
- Nature harbors crystals of dimensionality (d) only up to three. Here we introduce the notion of projected topological branes (PTBs): Lower-dimensional branes embedded in higher-dimensional parent topological crystals, constructed via a geometric cut-and-project procedure on the Hilbert space of the parent lattice Hamiltonian. When such a brane is inclined at a rational or an irrational slope, either a new lattice periodicity or a quasicrystal emerges. The latter gives birth to topoquasicrystals within the landscape of PTBs. As such PTBs are shown to inherit the hallmarks, such as the bulk-boundary and bulk-dislocation correspondences, and topological invariant, of the parent topological crystals. We exemplify these outcomes by focusing on two-dimensional parent Chern insulators, leaving its signatures on projected one-dimensional (1D) topological branes in terms of localized endpoint modes, dislocation modes and the local Chern number. Finally, by stacking 1D projected Chern insulators, we showcase the imprints of three-dimensional Weyl semimetals in d = 2, namely the Fermi arc surface states and bulk chiral zeroth Landau level, responsible for the chiral anomaly. Altogether, the proposed PTBs open a realistic avenue to harness higher-dimensional (d > 3) topological phases in laboratory. Authors introduce a new class of topological materials, namely projected topological branes that are holographic images of higher-dimensional topological crystals, and feature either emergent crystalline or aperiodic quasicrystalline order. They manifest bulk-boundary and bulk-lattice defect correspondences of parent crystals and open a realistic route to harness four and higher-dimensional topological crystals in three-dimensional world.
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| 42. |
- Pennacchietti, Matteo, et al.
(författare)
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Oscillating photonic Bell state from a semiconductor quantum dot for quantum key distribution
- 2024
-
Ingår i: Communications Physics. - : Springer Nature. - 2399-3650. ; 7:1
-
Tidskriftsartikel (refereegranskat)abstract
- An on-demand source of bright entangled photon pairs is desirable for quantum key distribution (QKD) and quantum repeaters. The leading candidate to generate such pairs is based on spontaneous parametric down-conversion (SPDC) in non-linear crystals. However, its pair extraction efficiency is limited to 0.1% when operating at near-unity fidelity due to multiphoton emission at high brightness. Quantum dots in photonic nanostructures can in principle overcome this limit, but the devices with high entanglement fidelity (99%) have low pair extraction efficiency (0.01%). Here, we show a measured peak entanglement fidelity of 97.5% ± 0.8% and pair extraction efficiency of 0.65% from an InAsP quantum dot in an InP photonic nanowire waveguide. We show that the generated oscillating two-photon Bell state can establish a secure key for peer-to-peer QKD. Using our time-resolved QKD scheme alleviates the need to remove the quantum dot energy splitting of the intermediate exciton states in the biexciton-exciton cascade.
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| 43. |
- Pietrini, Alberto, et al.
(författare)
-
A statistical approach to detect protein complexes at X-ray free electron laser facilities
- 2018
-
Ingår i: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 1
-
Tidskriftsartikel (refereegranskat)abstract
- The Flash X-ray Imaging (FXI) technique, under development at X-ray free electron lasers (XFEL), aims to achieve structure determination based on diffraction from individual macromolecular complexes. We report an FXI study on the first protein complex-RNA polymerase II-ever injected at an XFEL. A successful 3D reconstruction requires a high number of observations of the sample in various orientations. The measured diffraction signal for many shots can be comparable to background. Here we present a robust and highly sensitive hit-identification method based on automated modeling of beamline background through photon statistics. It can operate at controlled false positive hit-rate of 3 x10(-5). We demonstrate its power in determining particle hits and validate our findings against an independent hit-identification approach based on ion time-of-flight spectra. We also validate the advantages of our method over simpler hit-identification schemes via tests on other samples and using computer simulations, showing a doubled hit-identification power.
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| 44. |
- Rebolledo-Salgado, Israel, et al.
(författare)
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Platicon dynamics in photonic molecules
- 2023
-
Ingår i: Communications Physics. - : Nature Research. - 2399-3650. ; 6:1
-
Tidskriftsartikel (refereegranskat)abstract
- Coherent dissipative structures known as platicons can be reliably generated in photonic molecules, resulting in deterministic and reproducible microcombs derived from a continuous-wave pump. However, the supermode spectrum of standard photonic molecules displays numerous avoided mode crossings, distorting the spectral envelope of platicon microcombs. Here, we obtain a platicon microcomb using a photonic molecule configuration based on two coupled microcavities, whose size differs by an order of magnitude. This results in an engineered microcomb spectrum that closely resembles the one generated in an ideal single microresonator with just one frequency mode shift. We observe the coupling between the repetition rate of the platicon microcomb with the frequency of the pump laser, an effect originating from the dispersive-wave recoil induced by mode crossings. Using two identical platicon microcombs, we make use of such coupling to realize dual-comb interferometry. These results contribute to understanding dissipative structures in normal-dispersion microresonators and offer an alternative to applications such as spectroscopy and metrology.
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| 45. |
- Seibold, Goetz, et al.
(författare)
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Strange metal behaviour from charge density fluctuations in cuprates
- 2021
-
Ingår i: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 4:1
-
Tidskriftsartikel (refereegranskat)abstract
- Besides the mechanism responsible for high critical temperature superconductivity, the grand unresolved issue of the cuprates is the occurrence of a strange metallic state above the so-called pseudogap temperature T-*. Even though such state has been successfully described within a phenomenological scheme, the so-called Marginal Fermi-Liquid theory, a microscopic explanation is still missing. However, recent resonant X-ray scattering experiments identified a new class of charge density fluctuations characterized by low characteristic energies and short correlation lengths, which are related to the well-known charge density waves. These fluctuations are present over a wide region of the temperature-vs-doping phase diagram and extend well above T-*. Here we investigate the consequences of charge density fluctuations on the electron and transport properties and find that they can explain the strange metal phenomenology. Therefore, charge density fluctuations are likely the long-sought microscopic mechanism underlying the peculiarities of the metallic state of cuprates. The strange metallic state of cuprates occurring in a broad region of their phase diagram outside the superconducting and pseudogapped regions remains a mystery. Here the authors consider the charge density fluctuations recently discovered in resonant X-ray experiments as a possible source of scattering and show that these fluctuations can account for the strange metallic behavior.
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| 46. |
- Shaker, Kian, et al.
(författare)
-
Phase-contrast X-ray tomography resolves the terminal bronchioles in free-breathing mice
- 2021
-
Ingår i: Communications Physics. - : Springer Nature. - 2399-3650. ; 4:1
-
Tidskriftsartikel (refereegranskat)abstract
- Mechanical ventilation of living animals is routinely used to achieve high-resolution pulmonary imaging, but this can damage the subject. Here, an alternative, free-breathing method enables X-ray tomography with 30 mu m resolution. Phase-contrast X-ray lung imaging has broken new ground in preclinical respiratory research by improving contrast at air/tissue interfaces. To minimize blur from respiratory motion, intubation and mechanical ventilation is commonly employed for end-inspiration gated imaging at synchrotrons and in the laboratory. Inevitably, the prospect of ventilation induced lung injury (VILI) renders mechanical ventilation a confounding factor in respiratory studies of animal models. Here we demonstrate proof-of-principle 3D imaging of the tracheobronchial tree in free-breathing mice without mechanical ventilation at radiation levels compatible with longitudinal studies. We use a prospective gating approach for end-expiration propagation-based phase-contrast X-ray imaging where the natural breathing of the mouse dictates the acquisition flow. We achieve intrapulmonary spatial resolution in the 30-mu m-range, sufficient for resolving terminal bronchioles in the 60-mu m-range distinguished from the surrounding lung parenchyma. These results should enable non-invasive longitudinal studies of native state murine airways for translational lung disease research in the laboratory.
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| 47. |
- Simutis, Gediminas, et al.
(författare)
-
Single-domain stripe order in a high-temperature superconductor
- 2022
-
Ingår i: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 5:1
-
Tidskriftsartikel (refereegranskat)abstract
- The coupling of spin, charge and lattice degrees of freedom results in the emergence of novel states of matter across many classes of strongly correlated electron materials. A model example is unconventional superconductivity, which is widely believed to arise from the coupling of electrons via spin excitations. In cuprate high-temperature superconductors, the interplay of charge and spin degrees of freedom is also reflected in a zoo of charge and spin-density wave orders that are intertwined with superconductivity. A key question is whether the different types of density waves merely coexist or are indeed directly coupled. Here we profit from a neutron scattering technique with superior beam-focusing that allows us to probe the subtle spin-density wave order in the prototypical high-temperature superconductor La1.88Sr0.12CuO4 under applied uniaxial pressure to demonstrate that the two density waves respond to the external tuning parameter in the same manner. Our result shows that suitable models for high-temperature superconductivity must equally account for charge and spin degrees of freedom via uniaxial charge-spin stripe fluctuations.
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| 48. |
- Singh, G., et al.
(författare)
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Stoichiometric control of electron mobility and 2D superconductivity at LaAlO 3 -SrTiO 3 interfaces
- 2024
-
Ingår i: Communications Physics. - 2399-3650. ; 7:1
-
Tidskriftsartikel (refereegranskat)abstract
- SrTiO3-based conducting interfaces, which exhibit coexistence of gate-tunable 2D superconductivity and strong Rashba spin-orbit coupling (RSOC), are candidates to host topological superconductive phases. Yet, superconductivity is usually in the dirty limit, which tends to suppress nonconventional pairing and therefore challenges these expectations. Here we report on LaAlO3/SrTiO3 (LAO/STO) interfaces with large mobility and mean free paths comparable to the superconducting coherence length, approaching the clean limit for superconductivity. We further show that the carrier density, mobility, and formation of the superconducting condensate are controlled by the fine-tuning of La/Al chemical ratio in the LAO film. We find a region in the superconducting phase diagram where the critical temperature is not suppressed below the Lifshitz transition, at odds with previous experimental investigations. These findings point out the relevance of achieving a clean-limit regime to enhance the observation of unconventional pairing mechanisms in these systems.
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| 49. |
- Sobolev, Egor, et al.
(författare)
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Megahertz single-particle imaging at the European XFEL
- 2020
-
Ingår i: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 3:1
-
Tidskriftsartikel (refereegranskat)abstract
- The emergence of high repetition-rate X-ray free-electron lasers (XFELs) powered by superconducting accelerator technology enables the measurement of significantly more experimental data per day than was previously possible. The European XFEL is expected to provide 27,000 pulses per second, over two orders of magnitude more than any other XFEL. The increased pulse rate is a key enabling factor for single-particle X-ray diffractive imaging, which relies on averaging the weak diffraction signal from single biological particles. Taking full advantage of this new capability requires that all experimental steps, from sample preparation and delivery to the acquisition of diffraction patterns, are compatible with the increased pulse repetition rate. Here, we show that single-particle imaging can be performed using X-ray pulses at megahertz repetition rates. The results obtained pave the way towards exploiting high repetition-rate X-ray free-electron lasers for single-particle imaging at their full repetition rate.
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| 50. |
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