Evidence for the Formation of Quasi-Bound-State in an Asymmetrical Quantum Point Contact

TL;DR

This paper reports the observation of sharp resonance peaks and the destruction of the first conductance plateau in asymmetric quantum point contacts, suggesting the formation of a quasi-bound state stabilized by asymmetry-induced momentum mismatch.

Contribution

It provides experimental evidence for quasi-bound state formation in asymmetric QPCs, linking geometry to non-Fermi liquid behavior and conductance anomalies.

Findings

Sharp resonance peaks below the first conductance plateau

Complete destruction of the 2e^2/h conductance plateau under certain conditions

Temperature dependence indicating non-Fermi liquid behavior

Abstract

Features below the first conductance plateau in ballistic quantum point contacts (QPCs) are often ascribed to electron interaction and spin effects within the single mode limit. In QPCs with a highly asymmetric geometry, we observe sharp resonance peaks when the point contacts are gated to the single mode regime, and surprisingly, under certain gating conditions, a complete destruction of the 2e^2/h, first quantum plateau. The temperature evolution of the resonances suggest non-Fermi liquid behavior, while the overall nonlinear characterizations reveal features reminiscent of the 0.7 effect. We attribute these unusual behaviors to the formation of a quasi bound state, which is stabilized by a momentum-mismatch accentuated by asymmetry.