Evidence for a New Intermediate Phase in a Strongly Correlated 2D System near Wigner Crystallization

TL;DR

This study provides evidence for an intermediate phase in a strongly correlated 2D system near Wigner crystallization, revealing coexistence of Fermi liquid and incipient Wigner crystal states, challenging the notion of a sharp phase transition.

Contribution

It uncovers a mixed phase where Fermi liquid and Wigner crystal features coexist, suggesting a gradual transition rather than a sharp one in 2D strongly correlated systems.

Findings

Identification of a coexistence phase between Fermi liquid and Wigner crystal.

Observation of non-trivial temperature-dependent resistivity behavior.

Evidence supporting a gradual transition rather than a sharp phase change.

Abstract

How the two dimensional (2D) quantum Wigner crystal (WC) transforms into the metallic liquid phase remains to be an outstanding problem in physics. In theories considering the 2D WC to liquid transition in the clean limit, it was suggested that a number of intermediate phases might exist. We have studied the transformation between the metallic fluid phase and the low magnetic field reentrant insulating phase (RIP) which was interpreted as due to WC formation [Qiu et al, PRL 108, 106404 (2012)], in a strongly correlated 2D hole system with large interaction parameter $r_s$ ($\sim~$20-30) and high mobility. Instead of a sharp transition, we found that increasing density (or lowering $r_s$) drives the RIP into a state where the incipient RIP coexists with Fermi liquid. This apparent mixture phase intermediate between Fermi liquid and WC also exhibits a non-trivial temperature dependent resistivity behavior which may be qualitatively understood by the reversed melting of WC in the mixture, in analogy to the Pomeranchuk effect in the solid-liquid mixture of Helium-3.