arXiv subjects

Julia S. Meyer

Publications and source records attributed to Julia S. Meyer.

59 records · Page 4Linked to original sources

arXiv2002

Quantum in-plane magnetoresistance in 2D electron systems

We review various aspects of magnetoresistance in (quasi-)twodimensional systems subject to an in-plane magnetic field. Concentrating on single-particle effects, three mechanisms leading to magnetoresistance are discussed: the orbital effect of the magnetic field -- due to inter-subband mixing -- and the sensitivity of this effect to the geometrical symmetry of the system, the interplay between spin-orbit coupling and Zeeman splitting, and the influence of the field on spin scattering at magnetic impurities.

cond-mat.mes-hall↗

arXiv2001

Phase coherence phenomena in superconducting films

Superconducting films subject to an in-plane magnetic field exhibit a gapless superconducting phase. We explore the quasi-particle spectral properties of the gapless phase and comment on the transport properties. Of particular interest is the sensitivity of the quantum interference phenomena in this phase to the nature of the impurity scattering. We find that films subject to columnar defects exhibit a `Berry-Robnik' symmetry which changes the fundamental properties of the system. Furthermore, we explore the integrity of the gapped phase. As in the magnetic impurity system, we show that optimal fluctuations of the random impurity potential conspire with the in-plane magnetic field to induce a band of localized sub-gap states. Finally, we investigate the interplay of the proximity effect and gapless superconductivity in thin normal metal-superconductor bi-layers.

cond-mat.supr-con↗

arXiv2001

Magnetotunneling spectroscopy of mesoscopic correlations in two-dimensional electron systems

An approach to experimentally exploring electronic correlation functions in mesoscopic regimes is proposed. The idea is to monitor the mesoscopic fluctuations of a tunneling current flowing between the two layers of a semiconductor double-quantum-well structure. From the dependence of these fluctuations on external parameters, such as in-plane or perpendicular magnetic fields, external bias voltages, etc., the temporal and spatial dependence of various prominent correlation functions of mesoscopic physics can be determined. Due to the absence of spatially localized external probes, the method provides a way to explore the interplay of interaction and localization effects in two-dimensional systems within a relatively unperturbed environment. We describe the theoretical background of the approach and quantitatively discuss the behavior of the current fluctuations in diffusive and ergodic regimes. The influence of both various interaction mechanisms and localization effects on the current is discussed. Finally a proposal is made on how, at least in principle, the method may be used to experimentally determine the relevant critical exponents of localization-delocalization transitions.

cond-mat.mes-hall↗

arXiv2001

Gap Fluctuations in Inhomogeneous Superconductors

Spatial fluctuations of the effective pairing interaction between electrons in a superconductor induce variations of the order parameter which in turn lead to significant changes in the density of states. In addition to an overall reduction of the quasi-particle energy gap, theory suggests that mesoscopic fluctuations of the impurity potential induce localised tail states below the mean-field gap edge. Using a field theoretic approach, we elucidate the nature of the states in the `sub-gap' region. Specifically, we show that these states are associated with replica symmetry broken instanton solutions of the mean-field equations.

cond-mat.supr-con↗

arXiv2001

Quantum transport in parallel magnetic fields: A realization of the Berry-Robnik symmetry phenomenon

We analyze the magnetoconductance of two-dimensional electron and hole gases (2DEGs) subject to a parallel magnetic field. It is shown that, for confining potential wells which are symmetric with respect to spatial inversion, a temperature-dependent weak localization signal exists even in the presence of a magnetic field. Deviations from this symmetry lead to magnetoconductance profiles that contain information on both, the geometry of the confining potential and characteristics of the disorder.

cond-mat.mes-hall↗