| 1. |
- Amundsen, Morten, et al.
(författare)
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Grain-boundary topological superconductor
- 2023
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Ingår i: Communications Physics. - : Springer Nature. - 2399-3650. ; 6:1
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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
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Ingår i: Communications Physics. - : NATURE PORTFOLIO. - 2399-3650. ; 6:1
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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. |
- Choudhary, Akash, et al.
(författare)
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Orientational dynamics and rheology of active suspensions in weakly viscoelastic flows
- 2023
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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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| 4. |
- Crialesi-Esposito, Marco, et al.
(författare)
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The interaction of droplet dynamics and turbulence cascade
- 2023
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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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| 5. |
- 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
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Ingår i: Communications Physics. - 2399-3650. ; 6:1
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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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| 6. |
- Ge, Yuqing, 1996, et al.
(författare)
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Constructing coarse-grained skyrmion potentials from experimental data with Iterative Boltzmann Inversion
- 2023
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Ingår i: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 6:1
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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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| 7. |
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| 8. |
- Hansson, Tobias, et al.
(författare)
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Modeling of dual frequency combs and bistable solitons in third-harmonic generation
- 2023
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Ingår i: Communications Physics. - : NATURE PORTFOLIO. - 2399-3650. ; 6:1
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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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| 9. |
- 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
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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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| 10. |
- Jünger, Christian, et al.
(författare)
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Intermediate states in Andreev bound state fusion
- 2023
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Ingår i: Communications Physics. - 2399-3650. ; 6:1
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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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