Fluctuating spin density waves in metals

TL;DR

This paper extends a U(1) gauge theory to an SU(2) gauge framework to describe the complex phase transitions involving spin density waves and Fermi surface changes in metals, with implications for cuprate superconductors.

Contribution

It generalizes existing gauge theories to arbitrary band structures and introduces an SU(2) gauge theory to describe phase transitions in spin density wave metals.

Findings

Transition to large Fermi surface can be direct or via non-Fermi liquid phases.

The phase diagram includes fractionalized Fermi surfaces.

Application to cuprate phase diagrams is discussed.

Abstract

Recent work has used a U(1) gauge theory to describe the physics of Fermi pockets in the presence of fluctuating spin density wave order. We generalize this theory to an arbitrary band structure and ordering wavevector. The transition to the large Fermi surface state, without pockets induced by local spin density wave order, is described by embedding the U(1) gauge theory in a SU(2) gauge theory. The phase diagram of the SU(2) gauge theory shows that the onset of spin density wave order in the Fermi liquid occurs either directly, in the framework discussed by Hertz, or via intermediate non-Fermi liquid phases with Fermi surfaces of fractionalized excitations. We discuss application of our results to the phase diagram of the cuprates.