Singular non-ordering susceptibility at a Pomeranchuk instability

TL;DR

This paper investigates the behavior of magnetic susceptibilities near a Pomeranchuk instability in two-dimensional electron systems, revealing singularities and divergence patterns that have broad implications for related materials.

Contribution

It demonstrates that non-ordering susceptibilities exhibit singularities and divergences at critical points in systems with Pomeranchuk instabilities, extending understanding of critical fluctuations.

Findings

Longitudinal susceptibility chi^{zz} shows a jump at the critical point.

The magnitude of the jump diverges at a tricritical point.

Finite momentum scattering processes lead to divergence of chi^{zz} at critical points.

Abstract

We study magnetic susceptibilities of two-dimensional itinerant electron systems exhibiting symmetry-breaking Fermi surface distortions, the so-called d-wave Pomeranchuk instability, in a magnetic field. In a pure forward scattering model, the longitudinal susceptibility chi^{zz} is found to exhibit a jump at a critical point. The magnitude of this jump diverges at a tricritical point. When scattering processes involving finite momentum transfers are allowed for, chi^{zz} is expected to diverge also at a critical point. The system displays multiple critical fluctuations. We argue that the features of chi^{zz} are general properties associated with singularities of a non-ordering susceptibility, leading to implications for a variety of materials including Sr_3Ru_2O_7.