Classical and quantum liquids induced by quantum fluctuations

TL;DR

This paper investigates how quantum fluctuations influence classical degenerate states, revealing a quantum liquid phase in a frustrated lattice model and identifying a quantum critical point.

Contribution

It demonstrates the emergence of a quantum liquid phase from classical degeneracy in a coupled quantum-classical model on a triangular lattice.

Findings

Identification of a charge disordered quantum liquid phase

Existence of a crossover line ending in a quantum critical point

Insights into the quantum-classical transition in frustrated systems

Abstract

Geometrically frustrated interactions may render classical ground-states macroscopically degenerate. The connection between classical and quantum liquids and how the degeneracy is affected by quantum fluctuations is, however, less well understood. We study a simple model of coupled quantum and classical degrees of freedom, the so-called Falicov-Kimball model, on a triangular lattice and away from half-filling. For weak interactions the phase diagram features a charge disordered state down to zero temperature. We provide compelling evidence that this phase is a liquid and show that it is divided by a crossover line that terminates in a quantum critical point. Our results offer a new vantage point to address how quantum liquids can emerge from their classical counterparts.