Bound state-continuum resonance transition in a shallow quantum well

TL;DR

This paper investigates a transition from a bound state to a continuum resonance in shallow quantum wells, predicting observable capacitance jumps and explaining mobility drops via intersubband scattering, with implications for topological quantum computing.

Contribution

It introduces the concept of bound state-continuum resonance transition in shallow quantum wells and links it to experimental observations and mobility behavior.

Findings

Capacitance jump observed at BSCR transition

Mobility drop explained by intersubband scattering

Level-broadened continuum resonance mediates impurity effects

Abstract

We show a transition from a bound state to a continuum resonance in a shallow quantum well (QW) by electrostatic gating to bend the conduction band edge. This bound state-continuum resonance (BSCR) transition is particularly relevant in topological quantum computing platforms where shallow InAs QWs are used. We predict the observed capacitance jump and the parallel metal-insulator transition accompanied the BSCR transition. An experimental puzzle in shallow InAs QWs is the mobility drop at an electron density smaller than expected for the bound-state second subband occupation. We explain this puzzle as a result of intersubband scattering involving a level-broadened continuum resonance, mediated by screened Coulomb impurities.