Anomalous Conductance Quantization in the Inter-band Gap of a One-dimensional Channel

TL;DR

This paper investigates unusual conductance behavior in a one-dimensional metallic channel, revealing that inter-band coupling can cause conductance to exceed expected quantized values, challenging traditional single-carrier transmission models.

Contribution

It demonstrates theoretically that inter-band coupling leads to anomalous conductance enhancement, a departure from conventional Landauer quantization in ballistic channels.

Findings

Observation of conductance exceeding quantized units due to inter-band effects

Theoretical explanation linking conductance enhancement to sub-band coupling

Robust nonlinear conductance behavior across density ranges

Abstract

We report on a striking departure from the canonical step sequence of quantized conductance in a ballistic, quasi-one-dimensional metallic channel. Ideally, in such a structure, each sub-band population contributes its Landauer conductance quantum independently of the rest. In a picture based exclusively on coherent single-carrier transmission, unitary back-scattering can lower a conductance step below ideal, but it is absolutely impossible for it to enhance the ideal Landauer conductance of a sub-band. Precisely such an anomalous and robust nonlinear enhancement has already been observed over the whole density range between sub-band thresholds (de Picciotto R et al., Phys. Rev. Lett. 92, 036805 (2004) and J. Phys. Condens. Matter 20, 164204 (2008)). We show theoretically that the anomalous enhancement of ideal Landauer conductance is the hallmark of carrier transitions coupling the discrete sub-bands.