Regime Of Charge Transport Research Articles

Energy gap of intermediate-valentSmB6studied by point-contact spectroscopy

We have investigated the intermediate valence narrow-gap semiconductor ${\mathrm{SmB}}_{6}$ at low temperatures using both conventional spear-anvil type point contacts as well as mechanically controllable break junctions. The zero-bias conductance varied between less than $0.01 \ensuremath{\mu}\mathrm{S}$ and up to 1 mS. The position of the spectral anomalies, which are related to the different activation energies and band gaps of ${\mathrm{SmB}}_{6},$ did not depend on the the contact size. Two different regimes of charge transport could be distinguished: Contacts with large zero-bias conductance are in the diffusive Maxwell regime. They had spectra with only small nonlinearities. Contacts with small zero-bias conductance are in the tunneling regime. They had larger anomalies, but still indicating a finite $45%$ residual quasiparticle density of states at the Fermi level at low temperatures of $T=0.1 \mathrm{K}.$ The density of states derived from the tuneling spectra can be decomposed into two energy-dependent parts with ${E}_{g}=21 \mathrm{meV}$ and ${E}_{d}=4.5 \mathrm{meV}$ wide gaps, respectively.

Elastic scattering as a cause of quantum dephasing: the conductance of two-dimensional imperfect conductors

A method is proposed for studying wave and particle transport in disordered waveguide systems of dimension higher than unity by means of exact one-dimensionalization of the dynamic equations in the mode representation. As a particular case, the T=0 conductance of a two-dimensional quantum wire is calculated, which exhibits ohmic behaviour, with length-dependent conductivity, at any conductor length exceeding the electron quasi-classical mean free path. The unconventional diffusive regime of charge transport is found in the range of conductor lengths where the electrons are commonly considered as localized. In quantum wires with more than one conducting channel, each being identified with the extended waveguide mode, the inter-mode scattering is proven to serve as a phase-breaking mechanism that prevents interference localization without real inelasticity of interaction.

Regimes of charge transport across semiconductor junctions

Charge transport across break junctions of n-doped Ge has been investigated. We have found several different regimes of transport. Although all junctions reflect the density of states of the samples, to extract the bulk density of states only few junctions in a rather restricted range of parameters turned out to be useful.