Fractionalized Metal in a Falicov-Kimball Model

TL;DR

This paper uncovers a novel fractionalized metallic phase in a 2D Falicov-Kimball model characterized by a single-particle gap but gapless excitations, using quantum Monte Carlo simulations and duality with slave-spin theory.

Contribution

It introduces the concept of a fractionalized or orthogonal metal in this model, connecting it to slave-spin theory and identifying a phase transition to a Fermi liquid.

Findings

Discovery of a metallic phase with a single-particle gap and gapless excitations.

Identification of a duality linking the model to slave-spin theory.

Observation of an Ising phase transition at a critical temperature.

Abstract

Quantum Monte Carlo simulations reveal an exotic metallic phase with a single-particle gap but gapless spin and charge excitations and a nonsaturating resistivity in a two-dimensional SU(2) Falicov-Kimball model. An exact duality between this model and an unconstrained slave-spin theory leads to a classification of the phase as a fractionalized or orthogonal metal whose low-energy excitations have different quantum numbers than the original electrons. Whereas the fractionalized metal corresponds to the regime of disordered slave spins, the regime of ordered slave spins is a Fermi liquid. At a critical temperature, an Ising phase transition to a spontaneously generated constrained slave-spin theory of the Hubbard model is observed.