Zero-bias Anomaly of Quantum Point Contacts in the Low-Conductance Limit

TL;DR

This paper investigates the zero-bias conductance peak in quantum point contacts at extremely low conductance levels, revealing distinct magnetic and temperature behaviors that challenge existing theories.

Contribution

It provides the first detailed measurements of zero-bias peaks at conductance as low as 10^{-4}e^2/h and compares their properties to higher conductance regimes.

Findings

Zero-bias peaks persist down to 10^{-4}e^2/h conductance.

Magnetic and temperature dependencies differ from higher conductance cases.

Results challenge current theoretical models of low-density QPC transport.

Abstract

Most quantum point contacts (QPCs) fabricated in high-mobility 2D electron gases show a zero-bias conductance peak near pinchoff, but the origin of this peak remains a mystery. Previous experiments have primarily focused on the zero-bias peak at moderate conductance, in the range (1-2)e^2/h. Here, measurements are presented of zero-bias peaks that persist down to 10^{-4}e^2/h. Magnetic field and temperature dependencies of the zero-bias peak in the low-conductance limit are qualitatively different from the analogous phenomenology at higher conductance, with implications for existing theoretical models of transport in low-density QPCs.