Landau theory of compressible magnets near a quantum critical point

TL;DR

This paper uses Landau theory to analyze how coupling between magnetic order and the lattice causes first order transitions in compressible metallic magnets near a quantum critical point, highlighting the divergence of this coupling.

Contribution

It demonstrates that the magnetic-lattice coupling diverges near the quantum critical point, leading to first order transitions, and provides a numerical solution of the Landau equations without approximations.

Findings

Coupling to the lattice diverges near the quantum critical point.

First order transitions are driven by magnetic-lattice coupling.

The work helps distinguish lattice-driven transitions from other mechanisms.

Abstract

Landau theory is used to investigate the behaviour of a metallic magnet driven towards a quantum critical point by the application of pressure. The observed dependence of the transition temperature with pressure is used to show that the coupling of the magnetic order to the lattice diverges as the quantum critical point is approached. This means that a first order transition will occur in magnets (both ferromagnets and antiferromagnets) because of the coupling to the lattice. The Landau equations are solved numerically without further approximations. There are other mechanisms that can cause a first order transition so the significance of this work is that it will enable us to determine the extent to which any particular first order transition is driven by coupling to the lattice or if other causes are responsible.