Specific Heat of a Fractional Quantum Hall System

TL;DR

This study measures the specific heat of a fractional quantum Hall system, revealing exponential behavior at certain fillings and Fermi liquid behavior at half-filling, using a novel time-resolved phonon absorption method.

Contribution

First measurement of specific heat in a composite fermion system at filling factor 1/2 using time-resolved phonon absorption.

Findings

Exponential temperature dependence at fractional fillings consistent with quasi-particle gaps.

Linear temperature dependence at ν=1/2 consistent with Fermi liquid of composite fermions.

First direct measurement of specific heat in a composite fermion system.

Abstract

Using a time-resolved phonon absorption technique, we have measured the specific heat of a two-dimensional electron system in the fractional quantum Hall effect regime. For filling factors $\nu = 5/3, 4/3, 2/3, 3/5, 4/7, 2/5$ and 1/3 the specific heat displays a strong exponential temperature dependence in agreement with excitations across a quasi-particle gap. At filling factor $\nu = 1/2$ we were able to measure the specific heat of a composite fermion system for the first time. The observed linear temperature dependence on temperature down to $T = 0.14$ K agrees well with early predictions for a Fermi liquid of composite fermions.