Thermodynamic Compressibility of a Two-Dimensional Electron System: Signature of a Droplet State

TL;DR

This study measures the thermodynamic compressibility of a 2D electron system using a field-penetration method, revealing signatures of a droplet state that differ from previous hole system studies.

Contribution

It provides experimental evidence for the droplet state in a 2D electron system and applies a new formalism to describe its compressibility characteristics.

Findings

Compressibility behavior differs from 2D hole systems

Density and temperature dependencies are qualitatively distinct

Results align with droplet state formalism

Abstract

We have used a field-penetration method to measure thermodynamic compressibility of a moderately interacting two-dimensional electron system ($r_{s}$ $\approx$ 0.5-3) in a three terminal GaAs/AlGaAs device, fabricated with an epitaxial lift-off technique. We found that the density and temperature dependencies of the compressibility are qualitatively different from that observed in earlier studies of the 2D hole system, where interaction energies are considerably stronger. We show that the observed characteristics can be described by the recently developed formalism for compressibility of the droplet state.