Spinless composite fermions in an ultra-high quality strained Ge quantum well

TL;DR

This study reports the observation of fractional quantum Hall states in a high-quality strained Ge quantum well, demonstrating spinless composite fermions with quantized Hall resistance and specific effective mass measurements.

Contribution

It provides the first observation of spinless composite fermions in strained Ge quantum wells, with detailed measurements of fractional quantum Hall states and composite fermion properties.

Findings

Quantized Hall resistance at specific filling factors

Spinless composite fermions with effective mass ~0.4 m_e

All observed states are spin-polarized due to large Zeeman energy

Abstract

We report on an observation of a fractional quantum Hall effect in an ultra-high quality two-dimensional hole gas hosted in a strained Ge quantum well. The Hall resistance reveals precisely quantized plateaus and vanishing longitudinal resistance at filling factors $\nu = 2/3, 4/3$ and $5/3$. From the temperature dependence around $\nu = 3/2$ we obtain the composite fermion mass of $m^\star \approx 0.4\,m_e$, where $m_e$ is the mass of a free electron. Owing to large Zeeman energy, all observed states are spin-polarized and can be described in terms of spinless composite fermions.