Quantum Order-by-Disorder in Strongly Correlated Metals

TL;DR

This paper explores how quantum fluctuations can induce new phases in strongly correlated metals through an order-by-disorder mechanism, extending classical entropic force concepts to quantum systems.

Contribution

It applies the order-by-disorder concept to metallic systems, providing a new perspective on quantum fluctuation effects in strongly correlated materials.

Findings

Quantum fluctuations can stabilize new metallic phases.

Application of classical order-by-disorder ideas to quantum metals.

Discussion of recent progress and future prospects.

Abstract

Entropic forces in classical many-body systems, e.g. colloidal suspensions, can lead to the formation of new phases. Quantum fluctuations can have similar effects: spin fluctuations drive the superfluidity of Helium-3 and a similar mechanism operating in metals can give rise to superconductivity. It is conventional to discuss the latter in terms of the forces induced by the quantum fluctuations. However, focusing directly upon the free energy provides a useful alternative perspective in the classical case and can also be applied to study quantum fluctuations. Villain first developed this approach for insulating magnets and coined the term order-by-disorder to describe the observed effect. We discuss the application of this idea to metallic systems, recent progress made in doing so, and the broader prospects for the future.