Evidence of a first order phase transition between Wigner crystal and Bubble Phases of 2D electrons in higher Landau levels

TL;DR

This study provides experimental evidence of a first order phase transition between Wigner crystal and Bubble phases in a 2D electron system at specific filling factors, identified through microwave conductivity resonances.

Contribution

The paper reports the first observation of coexistence of two phases indicating a first order transition in higher Landau levels of 2D electrons.

Findings

Detection of two resonances indicating phase coexistence

Transition point estimated at filling factor 4.22

Evidence supports a first order phase transition

Abstract

For filling factors $\nu$ in the range between 4.16 and 4.28, we simultaneously detect {\it two} resonances in the real diagonal microwave conductivity of a two--dimensional electron system (2DES) at low temperature $T \approx 35$ mK. We attribute the resonances to Wigner crystal and Bubble phases of the 2DES in higher Landau Levels. For $\nu$ below and above this range, only single resonances are observed. The coexistence of both phases is taken as evidence of a first order phase transition. We estimate the transition point as $\nu=4.22$.