Effect of magnetic field on spontaneous Fermi surface symmetry breaking

TL;DR

This paper investigates how magnetic fields influence spontaneous Fermi surface symmetry breaking with d-wave symmetry, revealing phase transition behaviors and potential relevance to bilayer ruthenate Sr3Ru2O7.

Contribution

It introduces a mean-field model analyzing magnetic field effects on d-wave Pomeranchuk instability, highlighting the transition order changes and absence of quantum critical points.

Findings

Fermi surface symmetry breaking occurs in both spin bands near van Hove filling.

Transition changes from second to first order with decreasing temperature.

Magnetic field suppresses transition temperature but does not induce quantum critical points.

Abstract

We study magnetic field effects on spontaneous Fermi surface symmetry breaking with d-wave symmetry, the so-called d-wave "Pomeranchuk instability''. We use a mean-field model of electrons with a pure forward scattering interaction on a square lattice. When either the majority or the minority spin band is tuned close to the van Hove filling by a magnetic field, the Fermi surface symmetry breaking occurs in both bands, but with a different magnitude of the order parameter. The transition is typically of second order at high temperature and changes to first order at low temperature; the end points of the second order line are tricritical points. This qualitative picture does not change even in the limit of a large magnetic field, although the magnetic field substantially suppresses the transition temperature at the van Hove filling. The field produces neither a quantum critical point nor a quantum critical end point in our model. In the weak coupling limit, typical quantities characterizing the phase diagram have a field-independent single energy scale while its dimensionless coefficient varies with the field. The field-induced Fermi surface symmetry breaking is a promising scenario for the bilayer ruthenate Sr3Ru2O7, and future issues are discussed to establish such a scenario.