Fractional Quantum Hall States in a Ge Quantum Well

TL;DR

This study investigates fractional quantum Hall states in a strained germanium quantum well, revealing composite fermion states and analyzing edge state tunneling, with results aligning with theoretical predictions in certain Landau levels.

Contribution

It provides experimental evidence of fractional quantum Hall states in Ge quantum wells and analyzes edge state tunneling, expanding understanding of quantum Hall phenomena in this material.

Findings

Observation of quantum Hall states in the composite fermion family

Detection of a precursor signal at filling fraction 5/2

Edge state separation estimates align with electrostatic models in the lowest spin-polarized Landau level

Abstract

Measurements of the Hall and dissipative conductivity of a strained Ge quantum well on a SiGe/(001)Si substrate in the quantum Hall regime are reported. We find quantum Hall states in the Composite Fermion family and a precursor signal at filling fraction $\nu=5/2$. We analyse the results in terms of thermally activated quantum tunneling of carriers from one internal edge state to another across saddle points in the long range impurity potential. This shows that the gaps for different filling fractions closely follow the dependence predicted by theory. We also find that the estimates of the separation of the edge states at the saddle are in line with the expectations of an electrostatic model in the lowest spin-polarised Landau level (LL), but not in the spin-reversed LL where the density of quasiparticle states is not high enough to accommodate the carriers required.