SwePub - sökning: L773:0295 5075 OR L773:1286 48...

Numrering	Referens	Omslagsbild	Hitta
1.	Yousefian, Zakiyeh, et al. (författare) Orientational arrest in dense suspensions of elliptical particles under oscillatory shear flows 2021 Ingår i: EPL. - : IOP Publishing. - 0295-5075. ; 136:3 Tidskriftsartikel (refereegranskat)abstract We study the rheological response of dense suspensions of elliptical particles, with an aspect ratio equal to 3, under oscillatory shear flows and imposed pressure by numerical simulations. Like for the isotropic particles, we find that the oscillatory shear flows respect the Cox-Merz rule at large oscillatory strains but differ at low strains, with a lower viscosity than the steady shear and higher shear jamming packing fractions. However, unlike the isotropic cases (i.e., discs and spheres), frictionless ellipses get dynamically arrested in their initial orientational configuration at small oscillatory strains. We illustrate this by starting at two different configurations with different nematic order parameters and the average orientation of the particles. Surprisingly, the overall orientation in the frictionless case is uncoupled to the rheological response close to jamming, and the rheology is only controlled by the average number of contacts and the oscillatory strain. Having larger oscillatory strains or adding friction does, however, help the system escape these orientational arrested states, which are evolving to a disordered state independent of the initial configuration at low strains and ordered ones at large strains.
2.	Lundin, Joakim, 1978- (författare) An effective action approach to photon propagation on a magnetized background 2009 Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 87:3, s. 31001-31005 Tidskriftsartikel (refereegranskat)abstract A new explicit analytical form of the dispersion relation for photon propagation in the presence of a strong background magnetic field is derived within the effective action framework. The dispersion relation is expressed in terms of well-known special functions, and the treatment is exact within the linearization procedure, the one-loop approximation, and the soft photon approximation. The results are incorporated in a kinetic spin plasma description for the purpose of studying quantum electrodynamical effects of strongly magnetized plasmas. The results are applied to astrophysical examples.
3.	Bishop, Adrian, et al. (författare) Link Operations for Slowing the Spread of Disease in Complex Networks 2011 Ingår i: Europhysics letters. - : EPLA. - 0295-5075 .- 1286-4854. ; 95:1, s. 18005- Tidskriftsartikel (refereegranskat)abstract A variety of social, biological and communication networks can be modelled using graph theoretical tools. Similar graphical tools can be used to model the topology by which disease, errors, and/or other undesired phenomenon etc. is spread and propagated through such networks. Certain network operations are proposed in this work that can be used to slow the spread of diseases in complex network topologies. The approach considered in this work differs from existing techniques in that it is based on optimally removing (or immunizing) individual links in the network as opposed to individual nodes. A systematic algorithm is outlined to achieve this edgewise immunization via a relaxed convex optimization protocol.
4.	Rocha, Luis E C, 1981-, et al. (författare) The network organisation of consumer complaints 2010 Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 91:2, s. 28005-28011 Tidskriftsartikel (refereegranskat)abstract Interaction between consumers and companies can create conflict. When a consensus is unreachable there are legal authorities to resolve the case. This letter is a study of data from the Brazilian Department of Justice from which we build a bipartite network of categories of complaints linked to the companies receiving those complaints. We find the complaint categories organised in an hierarchical way where companies only get complaints of lower degree if they already got complaints of higher degree. The fraction of resolved complaints for a company appears to be nearly independent of the equity of the company but is positively correlated with the total number of complaints received. We construct feature vectors based on the edge-weight —the weight of an edge represents the times complaints of a category have been filed against that company— and use these vectors to study the similarity between the categories of complaints. From this analysis, we obtain trees mapping the hierarchical organisation of the complaints. We also apply principal component analysis to the set of feature vectors concluding that a reduction of the dimensionality of these from 8827 to 27 gives an optimal hierarchical representation.
5.	Ali, Shahid, et al. (författare) Instability of drift-like waves and cross-field charged particle transport in a nonuniform collisional quantum magnetoplasma 2007 Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 78:4, s. 45001- Tidskriftsartikel (refereegranskat)
6.	Aref, Thomas, 1980, et al. (författare) Andreev tunneling in charge pumping with SINIS turnstiles 2011 Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 96:3 Tidskriftsartikel (refereegranskat)abstract We present measurements on hybrid single-electron turnstiles with superconducting leads contacting a normal island (SINIS). We observe Andreev tunneling of electrons influencing the current plateau characteristics of the turnstiles under radio-frequency pumping. The data is well accounted for by numerical simulations. We verify the dependence of the Andreev tunneling rate on the turnstile's charging energy. Increasing the charging energy effectively suppresses the Andreev current.
7.	Atanasova, L., et al. (författare) g-factor Measurements at RISING: The Cases of 127Sn and 128Sn 2010 Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075. ; 91:4 Tidskriftsartikel (refereegranskat)abstract We report on g-factor measurements of the 19/2(+) T-1/2 = 4.5(3) mu s isomer in Sn-127 and the 10(+) T-1/2 = 2.69(23) mu s isomer in Sn-128. These isomers were produced and spin-aligned in relativistic heavy-ion fragmentation at GSI and were selected and separated by the GSI fragment separator ( FRS). The gamma-rays of the isomeric decay were detected by the RISING gamma-ray spectrometer. The method of time-differential perturbed angular distributions was utilized. The measured g-factors, g(19/2(+); Sn-127) =-0.17(2) and g(10(+); Sn-128)=-0.20(4), are compared with shell model calculations. The measured g-factors confirm the predominantly nu h(11/2)(-2) and nu(s(1/2)(-1) h(11/2)(-2)) character of the 10(+) and 19/2(-) isomers in Sn-128 and Sn-127, respectively. The results demonstrate the feasibility of the method for similar measurements in exotic neutron-rich nuclei. Copyright (C) EPLA, 2010
8.	Boikov, Iouri, 1949, et al. (författare) Atomic rearrangements at the TiO2-terminated (001)SrTiO3 surface and growth of thin LaMnO3 films 2013 Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 102:5 Tidskriftsartikel (refereegranskat)abstract SrTiO3 is commonly used as a substrate for growth of various oxide films. Different reconstructions at the SrTiO3 surface have been claimed. A question is whether these survive subsequent depositions of thin films and influence film properties. Medium energy ion scattering (MEIS) was used to probe structure and composition of the surface layer of a TiO2-terminated (001) SrTiO3 single-crystal substrate and 1-4 unit cell (u.c.) thick LaMnO3 epilayers. Aligned spectra indicate enrichment of Ti at the surface and a TiO2 double-layer (DL) configuration. The DL arrangement survives pulsed-laser deposition of LaMnO3 in a background of high oxygen pressure (5 x 10(-2) mbar) while it is destroyed at lower oxygen pressure (10(-4) mbar). Simulations of random MEIS spectra indicate substantial interdiffusion and La doping of the substrate surface but all interfaces are nevertheless insulating.
9.	Cattani, F., et al. (författare) Multihump soliton-like structures in interactions of lasers and Bose-Einstein condensates 2011 Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 94:5, s. 53003- Tidskriftsartikel (refereegranskat)abstract An investigation is made of multihump and periodic solutions of the semiclassical coupled equations describing laser radiation copropagating with a Bose-Einstein condensate. Solutions reminiscent of optical vector solitons have been found and have been used to gain understanding of the dynamics observed in the numerical simulations, in particular to shed light on the phenomenon of jet emission from a condensate interacting with a laser.
10.	Croy, Alexander, 1981, et al. (författare) Dynamics of a nanoscale rotor driven by single-electron tunneling 2012 Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 98:6 Tidskriftsartikel (refereegranskat)abstract We investigate theoretically the dynamics and the charge transport properties of a rod-shaped nanoscale rotor, which is driven by a similar mechanism as the nanomechanical single-electron transistor (NEMSET). We show that a static electric potential gradient can lead to self-excitation of oscillatory or continuous rotational motion. We identify the relevant parameters of the device and study the dependence of the dynamics on these parameters. We discuss how the dynamics are related to the measured current through the device. Notably, in the oscillatory regime we find a negative differential conductance. The current-voltage characteristics can be used to infer details of the surrounding environment which is responsible for damping.
11.	Eggl, E, et al. (författare) X-ray phase-contrast tomosynthesis of a human ex vivo breast slice with an inverse Compton x-ray source 2017 Ingår i: EPL. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 116, s. 1-7 Tidskriftsartikel (refereegranskat)
12.	Eriksson, Anders, 1975, et al. (författare) On the microscopic foundation of dissipative particle dynamics 2009 Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 86:4 Tidskriftsartikel (refereegranskat)abstract Mesoscopic-particle-based fluid models, such as dissipative particle dynamics, are usually assumed to be coarse-grained representations of an underlying microscopic fluid. A fundamental question is whether there exists a map from microscopic particles in these systems to the corresponding coarse-grained particles, such that the coarse-grained system has the same bulk and transport properties as the underlying system. In this letter, we investigate the coarse-graining of microscopic fluids using a Voronoi-type projection that has been suggested in several studies. The simulations show that the projection fails in defining coarse-grained particles that have a physically meaningful connection to the microscopic fluid. In particular, the Voronoi projection produces identical coarse-grained equilibrium properties when applied to systems with different microscopic interactions and different bulk properties. © EPLA, 2009
13.	Fittipaldi, R., et al. (författare) Superconductivity in Sr2RuO4-Sr3Ru2O7 eutectic crystals 2008 Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 83:2, s. Art. no. 27007- Tidskriftsartikel (refereegranskat)abstract Superconducting behavior has been observed in the Sr2RuO4-Sr3Ru2O7 eutectic system as grown by the flux-feeding floating-zone technique. A supercurrent flows across a single interface between Sr2RuO4 and Sr3Ru2O7 areas at distances that are far beyond those expected in a conventional proximity effect. The current-voltage characteristics within the Sr3Ru2O7 macrodomain, as extracted from the eutectic, exhibit signatures of superconductivity in the bilayered Sr3Ru2O7 region. Detailed microstructural, morphological and compositional analyses address issues on the concentration and the size of Sr2RuO4 inclusions within the Sr3Ru2O7 matrix. We speculate on the possibility of inhomogeneous superconductivity in the eutectic Sr3Ru2O7 and exotic pairing induced by the Sr2RuO4 inclusions. Copyright (C) EPLA, 2008.
14.	Fu, J., et al. (författare) Cone-beam differential phase-contrast laminography with x-ray tube source 2014 Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075. ; 106:6 Tidskriftsartikel (refereegranskat)abstract We report on an x-ray cone-beam differential phase-contrast computed laminography (DPC-CL) method for tomographic reconstruction of thin and lamellar objects. We describe the specific scan geometry of DPC-CL, which consists of a Talbot-Lau grating interferometer and a lab-based x-ray tube source, and derive a filtered back-projection (FBP) reconstruction algorithm. The experimental results of a flat sphere phantom and a piece of ham demonstrate the validity of the proposed technique. The existing DPC-CL methods are based on synchrotron sources and the parallel-beam geometry. In contrast, our approach adopts a more accessible x-ray tube source and a cone-beam geometry. Therefore it significantly widens the application range of phase-contrast laminography, particularly in practical laboratory settings, beyond applications at large-scale synchrotron facilities. Copyright (C) EPLA, 2014
15.	Gustafsson, Mats, et al. (författare) Physical bounds on the all-spectrum transmission through periodic arrays 2009 Ingår i: Physical Review Letters. - : IOP Publishing. - 1079-7114. ; 87:3, s. 1-34002 Tidskriftsartikel (refereegranskat)abstract We show that the blockage in transmission of a screen with a periodic microstructure integrated over all wavelengths is bounded by the static polarizability per unit area of the screen. Physical bounds on the co-polarized transmission coefficient over a wavelength interval are presented using only information from the zero-frequency properties of the microstructure. The theoretical results are compared to and verified by measurements on a screen composed of a large number of split ring resonators printed on a dielectric substrate.
16.	Kakashvili, Paata, 1978, et al. (författare) Enhanced Two-Channel Kondo Physics in a Quantum Box Device 2007 Ingår i: Europhysics Letters (EPL). - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 79:4 Tidskriftsartikel (refereegranskat)abstract We propose a design for a one-dimensional quantum box device where the charge fluctuations are described by an anisotropic two-channel Kondo model. The device consists of a quantum box in the Coulomb blockade regime, weakly coupled to a quantum wire by a single-mode point contact. The electron correlations in the wire produce strong back scattering at the contact, significantly increasing the Kondo temperature as compared to the case of non-interacting electrons. By employing boundary conformal field theory techniques we show that the differential capacitance of the box exhibits manifest two-channel Kondo scaling with temperature and gate voltage, uncontaminated by the one-dimensional electron correlations. We discuss the prospect to experimentally access the Kondo regime with this type of device.
17.	Kalaboukhov, Alexei, 1975, et al. (författare) Improved cationic stoichiometry and insulating behavior at the interface of LaAlO3/SrTiO3 formed at high oxygen pressure during pulsed-laser deposition 2011 Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 93:3 Tidskriftsartikel (refereegranskat)abstract Medium-energy ion spectroscopy, MEIS, and scanning transmission electron microscopy, STEM, were used to correlate the atomic structure of LaAlO3/SrTiO3 interfaces with their electrical properties. Interfaces were prepared at high (5x10(-2) mbar) and low (10(-4) mbar) oxygen pressure by pulsed-laser deposition. The high-oxygen-pressure heterostructures were insulating for all thicknesses while the low-oxygen-pressure ones became metallic for thicknesses above 4 unit cells. MEIS data show enhancement of the Sr surface peak and suppression of the La one in interfaces prepared at low oxygen pressure, which is interpreted as a La-Sr intermixing. The effect was considerably smaller in high-oxygen-pressure samples. Analysis of high-angle annular-dark-field STEM images of the LAO films also indicates intermixing between La and Sr in low-oxygen-pressure samples, supporting MEIS data. Our results reveal the important role of oxygen pressure on the formation of the interface electron gas. Copyright (C) EPLA, 2011
18.	Karlsson, Daniel, et al. (författare) Dynamical self-stabilization of the Mott insulator: Time evolution of the density and entanglement entropy of out-of-equilibrium cold fermion gases 2011 Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075. ; 93:2 Tidskriftsartikel (refereegranskat)abstract The time evolution of the out-of-equilibrium Mott insulator is investigated numerically through calculations of space-time-resolved density and entropy profiles resulting from the release of a gas of ultracold fermionic atoms from an optical trap. For adiabatic, moderate and sudden switching-off of the trapping potential, the out-of-equilibrium dynamics of the Mott insulator is found to differ profoundly from that of the band insulator and the metallic phase, displaying a self-induced stability that is robust within a wide range of densities, system sizes and interaction strengths. The connection between the entanglement entropy and changes of phase, known for equilibrium situations, is found to extend to the out-of-equilibrium regime. Finally, the relation between the system's long time behavior and the thermalization limit is analyzed. Copyright (C) EPLA, 2011
19.	Lindgren, Kristian, 1960 (författare) On the equivalence between stochastic baker's maps and two-dimensional spin systems 2010 Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 90:3, s. 30011 / 1-4 Tidskriftsartikel (refereegranskat)abstract We show that there is a class of stochastic bakers transformations that is equivalent to the class of equilibrium solutions of two-dimensional spin systems with finite interaction. The construction is such that the equilibrium distribution of the spin lattice is identical to the invariant measure in the corresponding bakers transformation. We illustrate the equivalence by deriving two stochastic bakers maps representing the Ising model at a temperature above and below the critical temperature, respectively. A calculation of the invariant measure and the free energy in the baker system is then shown to be in agreement with analytic results of the two-dimensional Ising model.
20.	Malkoc, Ognjen, et al. (författare) Full counting statistics of generic spin entangler with quantum dot-ferromagnet detectors 2014 Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075. ; 105:4 Tidskriftsartikel (refereegranskat)abstract Entanglement between spatially separated electrons in nanoscale transport is a fundamental property, yet to be demonstrated experimentally. Here we propose and analyse theoretically the transport statistics of a generic spin entangler coupled to a hybrid quantum dot-ferromagnet detector system. We show that the full distribution of charges arriving at the ferromagnetic terminals provides complete information on the spin state of the particles emitted by the entangler. This provides means for spin entanglement detection via electrical current correlations, with optimal measurement strategies depending on the a priori knowledge of ferromagnet polarization and spin-flip rates in the detector dots. The scheme is exemplified by applying it to Andreev and triple dot entanglers. Copyright (C) EPLA, 2014
21.	Novotny, T., et al. (författare) Bubble coalescence in breathing DNA: Two vicious walkers in opposite potentials 2007 Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 77:4 Tidskriftsartikel (refereegranskat)abstract We investigate the coalescence of two DNA bubbles initially located at weak segments and separated by a more stable barrier region in a designed construct of double-stranded DNA. The characteristic time for bubble coalescence and the corresponding distribution are derived, as well as the distribution of coalescence positions along the barrier. Below the melting temperature, we find a Kramers-type barrier crossing behaviour, while at high temperatures, the bubble corners perform drift-diffusion towards coalescence. The results are obtained by mapping the bubble dynamics on the problem of two vicious walkers in opposite potentials.
22.	Puig von Friesen, Marc, et al. (författare) Can we always get the entanglement entropy from the Kadanoff-Baym equations? The case of the T-matrix approximation 2011 Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075. ; 95:2 Tidskriftsartikel (refereegranskat)abstract We study the time-dependent transmission of entanglement entropy through an out-of-equilibrium model interacting device in a quantum transport set-up. The dynamics is performed via the Kadanoff-Baym equations within many-body perturbation theory. The double occupancy <(n) over cap (R dagger)(n) over cap (R down arrow)>, needed to determine the entanglement entropy, is obtained from the equations of motion of the single-particle Green's function. A remarkable result of our calculations is that <(n) over cap (R dagger)(n) over cap (R down arrow)> can become negative, thus not permitting to evaluate the entanglement entropy. This is a shortcoming of approximate, and yet conserving, many-body self-energies. Among the tested perturbation schemes, the T-matrix approximation stands out for two reasons: it compares well to exact results in the low-density regime and it always provides a non-negative <(n) over cap (R dagger)(n) over cap (R down arrow)> For the second part of this statement, we give an analytical proof. Finally, the transmission of entanglement across the device is diminished by interactions but can be amplified by a current flowing through the system. Copyright (C) EPLA, 2011
23.	Saarikoski, H., et al. (författare) Coreless vortices in rotating two-component quantum droplets 2010 Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075. ; 91:3 Tidskriftsartikel (refereegranskat)abstract The rotation of a quantum liquid induces vortices to carry angular momentum. When the system is composed of multiple components that are distinguishable from each other, vortex cores in one component may be filled by particles of the other component, and coreless vortices form. Based on evidence from computational methods, here we show that the formation of coreless vortices occurs very similarly for repulsively interacting bosons and fermions, largely independent of the form of the particle interactions. We further address the connection to the Halperin wave functions of non-polarized quantum Hall states. Copyright (c) EPLA, 2010
24.	Sjöberg, Daniel, et al. (författare) Physical bounds on the all-spectrum transmission through periodic arrays: oblique incidence 2010 Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075. ; 92, s. 1-34009 Rapport (övrigt vetenskapligt/konstnärligt)abstract The performance of a low-pass screen designed to block electromagnetic waves in a stop-band is shown to have an upper bound defined by the static electric and magnetic polarizability per unit area of the screen. The bound is easy to calculate for all angles of incidence and polarizations, and applies regardless of how complicated the screen's microstructure is. For a homogeneous dielectric sheet the bound for TM polarization is more restrictive than the bound for TE, but this is not generally true for a screen with microstructure. The results are verified by measurements and simulations of oblique transmission through an array of split ring resonators, printed on a dielectric substrate.
25.	Slutskin, A.A., et al. (författare) Non-Markovian decoherence of a two-level system weakly coupled to a bosonic bath 2011 Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 96:4, s. 4003- Tidskriftsartikel (refereegranskat)abstract The Bloch-Redfield equation is a common tool for studying the evolution ofqubit systems weakly coupled to the environment. We investigate the accuracy of the Bornapproximation underlying this equation. We find that the high-order terms in the perturbativeexpansion contain accumulating divergences that make straightforward Born approximationinappropriate. We develop a diagrammatic technique to formulate, and solve the improvedself-consistent Born approximation. This more accurate treatment reveals an exponential timedependentprefactor in the non-Markovian contribution dominating the qubit long-time relaxationfound in Di Vincenzo D. P. and Loss D., Phys. Rev. B, 71 (2005) 035318. At the same time, theassociated dephasing is not affected and is described by the Born-Markov approximation.
26.	Sonne, Gustav, 1982, et al. (författare) High-temperature excess current and quantum suppression of electronic backscattering 2008 Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 84 Tidskriftsartikel (refereegranskat)abstract We consider the electronic current through a one-dimensional conductor in the ballistic transport regime and show that the quantum oscillations of a weakly pinned single-scattering target results in a temperature- and bias-voltage independent excess current at large bias voltages. This is a genuine quantum effect on transport that derives from an exponential reduction of electron backscattering in the elastic channel due to quantum delocalisation of the scatterer and from a suppression of low-energy electron backscattering in the inelastic channels caused by the Pauli exclusion principle. We show that both the mass of the target and the frequency of its quantum vibrations can be measured by studying the differential conductance and the excess current. We apply our analysis to the particular case of a weakly pinned C60 molecule encapsulated by a single-wall carbon nanotube and find that the discussed phenomena are experimentally observable.
27.	Thuresson, A., et al. (författare) Anomalous temperature behavior in clay swelling due to ion-ion correlations 2016 Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075. ; 114:3 Tidskriftsartikel (refereegranskat)abstract We show, experimentally and theoretically, that swelling of both natural and refined clays has an anomalous temperature behavior depending on counterion valency. In an aqueous clay dispersion dominated by monovalent counterions the swelling pressure increases with temperature as expected from entropic arguments. In a clay with predominantly divalent counterions, the opposite behavior is found. The explanation is due to the fact that ion-ion correlations increase with temperature. Ion-ion correlations are important at strong electrostatic coupling and in an aqueous solution the dielectric permittivity, ϵr, drops with increased temperature, T, in such a way that the product ϵrT also decreases. Thus, the net effect is an increased coupling.
28.	Tomczak, Jan M., et al. (författare) Combined GW and dynamical mean-field theory: Dynamical screening effects in transition metal oxides 2012 Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075. ; 100:6 Tidskriftsartikel (refereegranskat)abstract We present the first dynamical implementation of the combined GW and dynamical mean-field scheme ("GW + DMFT") for first-principles calculations of the electronic properties of correlated materials. The application to the ternary transition metal oxide SrVO3 demonstrates that this scheme inherits the virtues of its two parent theories: a good description of the local low-energy correlation physics encoded in a renormalized quasi-particle band structure, spectral weight transfer to Hubbard bands, and the physics of screening driven by long-range Coulomb interactions. Our data is in good agreement with available photoemission and inverse photoemission spectra; our analysis leads to a reinterpretation of the commonly accepted "three-peak structure" as originating from orbital effects rather than from the electron addition peak within the t(2g) manifold. Copyright (c) EPLA, 2012
29.	Trulsson, Martin, et al. (författare) Quasi-universality in mixed salt-free counterion systems 2017 Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075. ; 118:1 Tidskriftsartikel (refereegranskat)abstract The screening of plate-plate interactions by counterions is an age-old problem. We revisit this classic question when counterions exhibit a distribution of charges. While it is expected that the long-distance regime of interactions is universal, the behaviour of the inter-plate pressure at smaller distances should a priori depend rather severely on the nature of the ionic mixture screening the plate charges. We show that this is not the case, and that for comparable Coulombic couplings, different systems exhibit a quasi-universal equation of state.
30.	van Gruijthuijsen, Kitty, et al. (författare) Direct comparison of SESANS and SAXS to measure colloidal interactions 2014 Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075. ; 106:2 Tidskriftsartikel (refereegranskat)abstract We present a systematic comparison of conventional small-angle X-ray scattering (SAXS) with the relatively new real-space technique, spin-echo small-angle neutron scattering (SESANS). We apply both techniques to colloidal suspensions where the particles interact as hard spheres, with electrostatic repulsions, or with polymer-induced depletion attractions. We successfully model the data sets with the appropriate colloid-colloid interaction potentials to determine the colloid radius, effective volume fraction, and surface charge, while illustrating the different representations of colloid structuring related to both techniques. Copyright (C) EPLA, 2014
31.	Vikström, Anton, 1986, et al. (författare) Hypersonic edge solitons in graphene under quantum Hall effect 2015 Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 112:4, s. 44004- Tidskriftsartikel (refereegranskat)abstract We consider a graphene sheet with a zigzag edge subject to a perpendicular magnetic field and investigate the evolution of in-plane elastic edge deformation. In such a system, resonant electronic edge states generate a strong Landau damping of low-amplitude acoustic edge waves with specific wave vectors. We study the propagation of a short hypersonic edge pulse in the case of a strong interaction with resonant electronic edge states. Using the resonance approximation, we derive the system of equations describing the evolution of the pulse and show that self-induced transparency can appear under certain conditions. As a consequence, pulses with particular profiles can travel without attenuation at a velocity different from that of sound.
32.	Yates, K.A., et al. (författare) Andreev spectroscopy of CrO2 thin films on TiO2 and Al2O3 2013 Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 103:6 Tidskriftsartikel (refereegranskat)abstract Here we analyse the spectroscopic information gathered at a number of single CrO2/Pb interfaces. We examine thin films requiring additional interfacial layers to generate long-range spin triplet proximity effect superconductivity (CrO2/TiO2) or not (CrO 2/Al2O3). We analyse the data using two theoretical models and explore the use of a parameter-free method to determine the agreement between the models and experimental observations, showing the necessary temperature range that would be required to make a definitive statement. The use of the excess current as a further tool to distinguish between models is also examined. The analysis of the spectra demonstrates that the temperature dependence of the normalised zero-bias conductance is independent of the substrate onto which the films are grown. This result has important implications for the engineering of interfaces required for the long-range spin triplet proximity effect. © Copyright EPLA, 2013.
33.	Grönlund, Andreas, 1974-, et al. (författare) Evolution of rogue waves in interacting wave systems 2009 Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 86:2, s. 24001- Tidskriftsartikel (refereegranskat)abstract Large-amplitude water waves on deep water have long been known in the seafaring community, and are the cause of great concern for, e.g., oil platform constructions. The concept of such freak waves is nowadays, thanks to satellite and radar measurements, well established within the scientific community. There are a number of important models and approaches for the theoretical description of such waves. By analyzing the scaling behavior of freak wave formation in a model of two interacting waves, described by two coupled non-linear Schrödinger equations, we show that there are two different dynamical scaling behaviors above and below a critical angle θc of the direction of the interacting waves, below which all wave systems evolve and display statistics similar to a wave system of non-interacting waves. The results equally apply to other systems described by the non-linear Schrödinger equations, and should be of interest when designing optical wave guides.
34.	Khrennikov, Andrei, 1958- (författare) Entanglement's dynamics from classical stochastic process 2009 Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 88:4, s. Article ID: 40005- Tidskriftsartikel (refereegranskat)abstract Entanglement is still one of the main mysteries of QM. In this note we show that entanglement and its dynamics can be described by classical (so to say "prequantum") stochastic processes. This construction supports the original Einstein's attempt to reduce entanglement to correlations induced by the preparation procedure.
35.	Lundh, Emil (författare) Rotating states for trapped bosons in an optical lattice 2008 Ingår i: Europhysics letters. - Les Ulis : European Physical Society. - 0295-5075 .- 1286-4854. ; 84:1, s. 10007- Tidskriftsartikel (refereegranskat)abstract Rotational states for trapped bosons in an optical lattice are studied in the framework of the Hubbard model. Critical frequencies are calculated and the main parameter regimes are identified. Transitions are observed from edge superfluids to vortex lattices with Mott insulating cores, and subsequently to lattices of interstitial vortices. The former transition coincides with the Mott transition. Changes in symmetry of the vortex lattices are observed as a function of lattice depth. Predictions for experimental signatures are presented.
36.	Nicolis, Catherine, et al. (författare) Return time statistics of extreme events in deterministic dynamical systems 2007 Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 80:4, s. 40003-40008 Tidskriftsartikel (refereegranskat)abstract It is shown that deterministic dynamics leaves a clearcut signature on the statistical properties of the return time of extreme events, giving rise to properties that are not accounted for by the classical statistical approach. Analytical expressions are derived, compared to those of classical statistical theory and applied to generic examples of dynamical systems giving rise to quasi-periodic, strongly chaotic and intermittent chaotic behaviors. Copyright (c) EPLA, 2007.
37.	Syrwid, Andrzej, et al. (författare) Can a bright soliton model reveal a genuine time crystal for a finite number of bosons? 2021 Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 134:6 Tidskriftsartikel (refereegranskat)abstract We analyze time crystal effects in a finite system of bosons which form a bright soliton clump on the Aharonov-Bohm ring. In the large particle number limit, N -> infinity, this setup corresponds to the Wilczek model, where it is known that the time crystal behavior cannot be observed in the ground state of the system because a spontaneously formed soliton does not move. Here, we show that while the spontaneous formation of a moving soliton in the ground state can occur for N < infinity, the soliton decays before it makes a single revolution along the ring and the time crystal dynamics is impossible.
38.	Stasiewicz, K., et al. (författare) Acceleration of solar wind ions to 1 MeV by electromagnetic structures upstream of the Earth's bow shock 2013 Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 102:4, s. 49001- Tidskriftsartikel (refereegranskat)abstract We present measurements from the ESA/NASA Cluster mission that show in situ acceleration of ions to energies of 1MeV outside the bow shock. The observed heating can be associated with the presence of electromagnetic structures with strong spatial gradients of the electric field that lead to ion gyro-phase breaking and to the onset of chaos in ion trajectories. It results in rapid, stochastic acceleration of ions in the direction perpendicular to the ambient magnetic field. The electric potential of the structures can be compared to a field of moguls on a ski slope, capable of accelerating and ejecting the fast running skiers out of piste. This mechanism may represent the universal mechanism for perpendicular acceleration and heating of ions in the magnetosphere, the solar corona and in astrophysical plasmas. This is also a basic mechanism that can limit steepening of nonlinear electromagnetic structures at shocks and foreshocks in collisionless plasmas.
39.	Hansen, P. G., et al. (författare) The Neutron Halo of Extremely Neutron-Rich Nuclei 1987 Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 4:4, s. 409-414 Tidskriftsartikel (refereegranskat)abstract Empirical evidence suggests that neutron pairing plays an important role for the stability of nuclei near the neutron drip line. It is shown that the low binding of these nuclei will lead to a neutronization of the nuclear surface and possibly to large cross-sections for Coulomb dissociation, which then offers a new way to study clusters and their binding energies.
40.	Kikas, A., et al. (författare) Auger Spectra of K+ L23 Excitations in Potassium Halides 1991 Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 15:6, s. 683-686 Tidskriftsartikel (refereegranskat)abstract The L23M23M23 Auger spectra of K+ L23 excitation in potassium halides are measured using photon excitation with different energies in the region of the K+ L23 absorption edge (around 300 eV). It is shown that the screening of the two 3p holes caused by the collapsed 3d electron of the K+ L23 exciton leads to a considerable shift (by about (6÷7) eV) of the K+ L23M23M23 Auger bands to higher energies. Only the low-energy component of the crystal-field-split K+ 3d orbital forms a genuine bound state with 2p holes, whereas its high-energy component lies in the conduction band continuum and behaves like a shape resonance.
41.	Phuyal, Dibya, et al. (författare) The origin of low bandgap and ferroelectricity of a co-doped BaTiO3 2018 Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 124:2 Tidskriftsartikel (refereegranskat)abstract We recently demonstrated the lowest bandgap bulk ferroelectric material, BaTi1-x(Mn1/2Nb1/2)xO3, a promising candidate material for visible light absorption in opto- electronic devices. Using a combination of x-ray spectroscopies and density functional theory (DFT) calculations, we here elucidate this compound’s electronic structure and the modifications induced by Mn doping. In particular, we are able to rationalize how this compound retains its ferroelectricity even through a significant reduction of the optical gap upon Mn doping. The local electronic structure and atomic coordination are investigated using x-ray absorption at the Ti K, Mn K, and O K edges, which suggests only small distortions to the parent tetragonal ferroelectric system, BaTiO3, thereby providing a clue to the substantial retention of ferroelectricity in spite of doping. Features at the Ti K edge, which are sensitive to local symmetry and an indication of Ti off-centering within the Ti-O6 octahedra, show modest changes with doping and strongly corroborates with our measured polarization values. Resonant photoelectron spectroscopy results suggest the origin of the reduction of the bandgap in terms of newly created Mn d bands that hybridize with O 2p states. X-ray absorption spectra at the O K-edge provide evidence for new states below the conduction band of the parent compound, illustrating additional contributions facilitating bandgap reduction.
42.	Dobroliubov, M., et al. (författare) The Superfluidity and Experimental Properties of Odd-Energy-Gap Superconductors 1993 Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 26:2 Tidskriftsartikel (refereegranskat)
43.	Nisar, Jawad, et al. (författare) Stabilizing the defect-induced dilute magnetic semiconductors : Li-doping in GaN with Ga vacancies 2011 Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 93:5, s. 57006- Tidskriftsartikel (refereegranskat)abstract By means of first-principles calculations, we have investigated the effects of various Li-doping on the exchange interaction and the formation energy in bulk GaN with Ga vacancies. Although the Ga vacancies can induce ferromagnetism in GaN, their formation energy is rather high. Our calculations show that Li-doping can effectively tune the formation energy of Ga vacancies. It is revealed that the stabilizing effect depends on whether the number of holes is increased or decreased after Li-doping. When Li atoms substitutes for N atoms or occupies the interstitial sites, the holes are reduced and the formation energy of Ga vacancies is lowered. In contrast, Li substituting for Ga generates additional holes in the system, leading to an enhancement of the formation energy of Ga vacancies and making the system less stable. Copyright (c) EPLA, 2011
44.	Carbone, Francesco, et al. (författare) Chaotic advection and particle pairs diffusion in a low-dimensional truncation of two-dimensional magnetohydrodynamics 2022 Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 138:5 Tidskriftsartikel (refereegranskat)abstract The chaotic advection of fluid particle pairs is investigated though a low-order model of two-dimensional magnetohydrodynamic (MHD), where only five nonlinearly interacting modes are retained. The model is inthrinsically inhomogeneous and anisotropic because of the influence of large-scale fluctuations. Therefore, even though dynamically chaotic, the fields are unable to form the typical scaling laws of fully developed turbulence. Results show that a super-ballistic dynamics, reminiscent of the Richardson law of particle-pairs diffusion in turbulent flows, is robustly obtained using the truncated model. Indeed, even in the strongly reduced truncation presented here, particle diffusion in MHD turbulence has the same laws as the separation of velocity of particle pairs. The inherent anisotropy only affects the scaling of diffusivity, by enhancing the diffusion properties along one direction for small time-scales. Finally, when further anisotropy is introduced in the system through Alfven waves, fluid particles are trapped by these, and super-ballistic diffusion is replaced by Brownian-like diffusion. On the other hand, when the magnetic field is removed, the kinetic counterpart of the model does not show super-ballistic dynamics.
45.	Corbae, Paul, et al. (författare) Amorphous topological matter : Theory and experiment 2023 Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 142:1, s. 16001- Tidskriftsartikel (refereegranskat)abstract Topological phases of matter are ubiquitous in crystals, but less is known about their existence in amorphous systems, that lack long-range order. We review the recent progress made on defining amorphous topological phases, their new phenomenology. We discuss the open questions in the field which promise to significantly enlarge the set of materials and synthetic systems benefiting from the robustness of topological matter.
46.	Lei, Qinghua, et al. (författare) Anderson localisation and reentrant delocalisation of tensorial elastic waves in two-dimensional fractured media 2021 Ingår i: Europhysics letters. - : Institute of Physics Publishing (IOPP). - 0295-5075 .- 1286-4854. ; 136:3 Tidskriftsartikel (refereegranskat)abstract We study tensorial elastic wave transport in two-dimensional densely fractured media using numerical simulations and document transitions from propagation to diffusion and to localisation/delocalisation. For large fracture stiffness, waves are propagative at the scale of the system. For small stiffness, multiple scattering prevails, such that waves are diffusive in disconnected fracture networks, and localised in connected ones with a strong multifractality of the intensity field. A re-entrant delocalisation is found in well-connected fracture networks due to energy leakage via evanescent waves and cascades of mode conversion.
47.	Lucco Castello, Federico, et al. (författare) Classical bridge functions in classical and quantum plasma liquids 2022 Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 138:4 Tidskriftsartikel (refereegranskat)abstract Bridge functions, the missing link in the exact description of strong correlations, are indirectly extracted from specially designed molecular dynamics simulations of classical one-component plasma liquids and accurately parameterized. Their incorporation into an advanced integral equation theory description of Yukawa one-component plasma liquids and a novel dielectric formalism scheme for quantum one-component plasma liquids lead to an unprecedented agreement with available molecular dynamics simulations and new ab initio path integral Monte Carlo simulations, respectively. open access Copyright
48.	Mandal, Ipsita, et al. (författare) Robust quantum transport at particle-hole symmetry 2021 Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 135:1 Tidskriftsartikel (refereegranskat)abstract We study quantum transport in disordered systems with particle-hole symmetric Hamiltonians. The particle-hole symmetry is spontaneously broken after averaging with respect to disorder, and the resulting massless mode is treated in a random-phase representation of the invariant measure of the symmetry group. We compute the resulting fermionic functional integral of the average two-particle Green's function in a perturbation theory around the diffusive limit. The results up to two-loop order show that the corrections vanish, indicating that the diffusive quantum transport is robust. On the other hand, the diffusion coefficient depends strongly on the particle-hole symmetric Hamiltonian we choose to study. This reveals a connection between the underlying microscopic theory and the classical long-scale metallic behaviour of these systems.
49.	Saha, Sudarshan, et al. (författare) Multiple higher-order topological phases with even and odd pairs of zero-energy corner modes in a C-3 symmetry broken model 2023 Ingår i: Europhysics letters. - : Institute of Physics (IOP). - 0295-5075 .- 1286-4854. ; 142:5 Tidskriftsartikel (refereegranskat)abstract Here we study emergent higher-order topological (HOTI) phases in the extended Haldane model without C-3 symmetry. For the inversion symmetric case, the QSHI and QAHI phases can embed the HOTI phases while the remaining QASHI phase does not yield any HOTI phases. Remarkably, four-fold degeneracy of zero-energy corner states can be reduced to two-fold under the application (withdrawal) of sub-lattice mass (Zeeman field) term. The sub-lattice mass and Zeeman field terms compete with each other to pin down the two mid-gap states at zero-energy. Interestingly, the bulk polarization can topologically characterize the second-order topological insulator phase with the mid-gap corner modes irrespective of their energies as long as inversion symmetry is preserved. Our study indicates that a hybrid symmetry can in principle protect the second-order topological insulator phases, however, spin-spectrum gap has to be essentially finite there.
50.	Sernelius, Bo E (författare) Saturation effects in experiments on the thermal Casimir effect 2009 Ingår i: EPL. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 87:1, s. 14004- Tidskriftsartikel (refereegranskat)abstract We address three different problematic Casimir experiments in this work. The first is the classical Casimir force measured between two metal half-spaces; here in the form of the Casimir pressure measurement between a gold sphere and a gold plate as performed by Decca et al. (Phys. Rev. D, 75 (2007) 077101); theory predicts a large negative thermal correction, absent in the high-precision experiment. The second experiment is the measurement of the Casimir force between a metal plate and a laser irradiated semiconductor membrane as performed by Chen et al. (Phys. Rev. B, 76 (2007) 035338); the change in force with laser intensity is larger than predicted by theory. The third experiment is the measurement of the Casimir force between an atom and a wall in the form of the measurement by Obrecht et al. (Phys. Rev. Lett., 98 (2007) 063201) of the change in oscillation frequency of a Rb-87 Bose-Einstein condensate trapped to a fused silica wall; the change is smaller than predicted by theory. We show that saturation effects can explain the discrepancies between theory and experiment observed in all these cases.

Skapa referenser, mejla, bekava och länka

Länka till träfflistan

Träfflista för sökning "L773:0295 5075 OR L773:1286 4854 "

Avgränsa träffmängd

År