Quantum ballistic transport in constrictions of n-PbTe

TL;DR

This study investigates quantum ballistic transport in PbTe constrictions, revealing conductance quantization at high magnetic fields and temperature-independent steps at zero field, suggesting electron exchange interactions influence quantization.

Contribution

It demonstrates quantized conductance in PbTe constrictions at high magnetic fields and proposes a novel explanation involving exchange interactions at zero field.

Findings

Conductance quantization observed at B>1T in units of e^2/h.

Temperature-independent conductance steps of approximately e^2/h at zero field.

Potential role of exchange interactions in lifting Kramers degeneracy.

Abstract

Conductance of submicron constrictions of PbTe:Bi was studied up to 8T and between 4.2K and 50mK. The structures were fabricated by electron beam lithography and chemical etching of high--electron mobility films grown by MBE on BaF_2. In the moderately strong magnetic fields perpendicular to the current, B>1T, the conductance shows accurate quantization in the units of 1e^2/h as a function of the side-gate voltage. In the absence of the field, a temperature-independent step structure, with an average step height approx. 1e^2/h, is observed. It is suggested that such a quantization may reflect the lifting of the Kramers degeneracy by the exchange interaction among the electrons, effective despite a large dielectric constant of bulk PbTe.