arXiv subjects

S. Kettemann

Publications and source records attributed to S. Kettemann.

22 records · Page 2Linked to original sources

arXiv2003

Dimensional Crossover of Localisation and Delocalisation in a Quantum Hall Bar

The 2-- to 1--dimensional crossover of the localisation length of electrons confined to a disordered quantum wire of finite width $L_y$ is studied in a model of electrons moving in the potential of uncorrelated impurities. An analytical formula for the localisation length is derived, describing the dimensional crossover as function of width $L_y$, conductance $g$ and perpendicular magnetic field $B$ . On the basis of these results, the scaling analysis of the quantum Hall effect in high Landau levels, and the delocalisation transition in a quantum Hall wire are reconsidered.

cond-mat.mes-hall↗

arXiv2003

Localization Length in Anderson Insulator with Kondo Impurities

The localization length, $ξ$, in a 2--dimensional Anderson insulator depends on the electron spin scattering rate by magnetic impurities, $τ_s^{-1}$. For antiferromagnetic sign of the exchange, %constant, the time $τ_s$ is {\em itself a function of $ξ$}, due to the Kondo correlations. We demonstrate that the unitary regime of localization is impossible when the concentration of magnetic impurities, $n_{\tiny M}$, is smaller than a critical value, $n_c$. For $n_{\tiny M}>n_c$, the dependence of $ξ$ on the dimensionless conductance, $g$, is {\em reentrant}, crossing over to unitary, and back to orthogonal behavior upon increasing $g$. Sensitivity of Kondo correlations to a weak {\em parallel} magnetic field results in a giant parallel magnetoresistance.

cond-mat.mes-hall↗

arXiv1996

Characterization of Quantum Chaos by the Autocorrelation Function of Spectral Determinants

The autocorrelation function of spectral determinants is proposed as a convenient tool for the characterization of spectral statistics in general, and for the study of the intimate link between quantum chaos and random matrix theory, in particular. For this purpose, the correlation functions of spectral determinants are evaluated for various random matrix ensembles, and are compared with the corresponding semiclassical expressions. The method is demonstrated by applying it to the spectra of the quantized Sinai billiards in two and three dimensions.

chao-dyn↗

arXiv1994

Diamagnetic Response due to Localization in Chains of Connected Mesoscopic Rings

A dynamic response to a magnetic field of a chain of connected mesoscopic rings is considered. We show that the low frequency behavior corresponds to localization of the elctrons along the chain and to diamagnetic dynamic currents inside rings. The magnetization density due to these currents does not vanish even in the limit of the infinitely long chain of strongly connected rings. showing that this is a macroscopic effect. Being of a dynamic origin the currents can be destroyed by inelastic scattering, but we argue that the corresponding decay time can at low enough temperatures be large compared to all other time scales of the system. We suggest to check our results by measuring the magnetization of an ensemble of chains of connected rings in the diffusive regime or alternatively of linear antidot lattices where the mean free path due to elastic scattering is smaller than the superlattice spacing. This yields a new contactless method of studying the localization.

cond-mat↗