Quantum criticality in itinerant metamagnets

TL;DR

This paper investigates the critical thermodynamics near a metamagnetic quantum critical endpoint in metals using spin-fluctuation theory, revealing temperature-dependent behaviors and instabilities due to magnetoelastic coupling.

Contribution

It provides a detailed analysis of the effective potential for the Ising order parameter and its temperature dependence, advancing understanding of quantum criticality in itinerant metamagnets.

Findings

Magnetization, specific heat, and susceptibility depend on H and T near QCEP.

Crossover lines in the (H,T) phase diagram are characterized.

QCEP is inherently unstable due to magnetoelastic effects.

Abstract

Critical thermodynamics close to a metamagnetic quantum critical endpoint (QCEP) in a metal is discussed within the framework of spin-fluctuation theory. We analyze the effective potential for the Ising order parameter that is renormalized by spin-fluctuations and acquires a characteristic temperature dependence. The resulting magnetic field, H, and temperature, T, dependence of the magnetization, specific heat, thermal expansion, magnetostriction, susceptibility and the Gr\"uneisen parameter are determined, and the crossover lines in the (H,T) phase diagram are specified. We point out that the metamagnetic QCEP is intrinsically unstable with respect to a magnetoelastic coupling.