Orthogonal Metals: The simplest non-Fermi liquids

TL;DR

This paper introduces the Orthogonal Metal, a novel non-Fermi liquid phase that mimics Fermi liquids in some properties but differs in electron spectral functions, and explores its transition from Fermi liquids.

Contribution

It presents the concept of Orthogonal Metals, constructs wavefunctions for this phase, and provides exactly soluble models illustrating the phase transition from Fermi liquids.

Findings

Orthogonal Metal has identical conductivity and thermodynamics as Fermi liquids.

Transition to Orthogonal Metal can be continuous with a critical Fermi surface.

Exactly soluble models demonstrate the phase transition and properties of Orthogonal Metals.

Abstract

We present a fractionalized metallic phase which is indistinguishable from the Fermi liquid in conductivity and thermodynamics, but is sharply distinct in one electron properties, such as the electron spectral function. We dub this phase the `Orthogonal Metal.' The Orthogonal Metal and the transition to it from the Fermi liquid are naturally described using a slave particle representation wherein the electron is expressed as a product of a fermion and a slave Ising spin. We emphasize that when the slave spins are disordered the result is not a Mott insulator (as erroneously assumed in the prior literature) but rather the Orthogonal Metal. We construct prototypical ground state wavefunctions for the Orthogonal Metal by modifying the Jastrow factor of Slater-Jastrow wavefunctions that describe ordinary Fermi liquids. We further demonstrate that the transition from the Fermi liquid to the Orthogonal Metal can, in some circumstances, provide a simple example of a continuous destruction of a Fermi surface with a critical Fermi surface appearing right at the critical point. We present exactly soluble models that realize an Orthogonal Metal phase, and the phase transition to the Fermi liquid. These models thus provide valuable solvable examples for phase transitions associated with the death of a Fermi surface.