Origins of conductance anomalies in a p-type GaAs quantum point contact

TL;DR

This study investigates conductance anomalies in a p-GaAs quantum point contact, identifying different origins and their behaviors through experimental gating techniques and finite bias measurements, supported by a two-impurity Kondo model.

Contribution

It introduces a method to distinguish local and generic conductance anomalies and proposes a model linking anomalies to localized states and impurity interactions.

Findings

The 0.7 anomaly remains unaffected by gate configuration changes.

Additional conductance features depend on gate voltage and are linked to localized states.

Finite bias measurements support a two-impurity Kondo interaction explanation.

Abstract

Low temperature transport measurements on a p-GaAs quantum point contact are presented which reveal the presence of a conductance anomaly that is markedly different from the conventional `0.7 anomaly'. A lateral shift by asymmetric gating of the conducting channel is utilized to identify and separate different conductance anomalies of local and generic origins experimentally. While the more generic 0.7 anomaly is not directly affected by changing the gate configuration, a model is proposed which attributes the additional conductance features to a gate-dependent coupling of the propagating states to localized states emerging due to a nearby potential imperfection. Finite bias conductivity measurements reveal the interplay between the two anomalies consistently with a two-impurity Kondo model.