Activated Behavior of the 0.7 2(e^2)/h Conductance Anomaly in Quantum Point Contacts

TL;DR

This paper experimentally investigates the 0.7 conductance anomaly in GaAs quantum point contacts, revealing it is due to a density-dependent excitation gap, consistent across different measurement conditions.

Contribution

It demonstrates that the 0.7 anomaly's activated behavior and the 0.9 anomaly are caused by the same density-dependent excitation gap, unifying different observations.

Findings

The 0.7 anomaly shows activated temperature dependence.

The 0.9 anomaly at finite bias is related to the same excitation gap.

Both anomalies originate from a density-dependent excitation gap.

Abstract

The 0.7 conductance anomaly in the quantized conductance of trench etched GaAs quantum point contacts is studied experimentally. The temperature dependence of the anomaly measured with vanishing source-drain bias reveals the same activated behavior as reported earlier for top-gated structures. Our main result is that the zero bias, high temperature 0.7 anomaly found in activation measurements and the finite bias, low temperature 0.9 anomaly found in transport spectroscopy have the same origin: a density dependent excitation gap.