Evidence for localization and 0.7 anomaly in hole quantum point contacts

TL;DR

This study demonstrates the presence of the 0.7 conductance anomaly in hole-based quantum point contacts, supporting the theory of charge localization as its origin, and shows its robustness under various conditions.

Contribution

It provides experimental evidence of the 0.7 anomaly in p-type GaAs/AlGaAs quantum point contacts, highlighting the role of charge localization in this phenomenon.

Findings

Observation of a 0.7 conductance plateau in hole quantum point contacts.

High magnetic fields reveal a quasi-localized state associated with the anomaly.

The 0.7 anomaly persists under lateral electric fields, indicating intrinsic physics.

Abstract

Quantum point contacts implemented in p-type GaAs/AlGaAs heterostructures are investigated by low-temperature electrical conductance spectroscopy measurements. Besides one-dimensional conductance quantization in units of $2e^{2}/h$ a pronounced extra plateau is found at about $0.7(2e^{2}/h)$ which possesses the characteristic properties of the so-called "0.7 anomaly" known from experiments with n-type samples. The evolution of the 0.7 plateau in high perpendicular magnetic field reveals the existence of a quasi-localized state and supports the explanation of the 0.7 anomaly based on self-consistent charge localization. These observations are robust when lateral electrical fields are applied which shift the relative position of the electron wavefunction in the quantum point contact, testifying to the intrinsic nature of the underlying physics.