# Orthogonal metal in the Hubbard model with liberated slave spins

## TL;DR

This paper investigates a fractionalized metallic phase in a two-dimensional Hubbard model using quantum Monte Carlo simulations, revealing unique properties of orthogonal metals and the effects of slave-spin constraints.

## Contribution

It provides a detailed numerical study of the orthogonal metal phase in the Hubbard model with slave spins, highlighting differences from mean-field theories and exploring the role of local constraints.

## Key findings

- Identification of a fractionalized metallic phase with a single-particle gap and gapless excitations.
- Differences between the observed phase and predictions from mean-field models.
- Absence of $ ext{pi}$-flux configurations in the slave-spin formulation.

## Abstract

A two-dimensional Falicov-Kimball model, equivalent to the Hubbard model in an unconstrained slave-spin representation, is studied by quantum Monte Carlo simulations. The focus is on a fractionalized metallic phase that is characterized in terms of spectral, thermodynamic, and transport properties, including a comparison to the half-filled Hubbard model. The properties of this phase, most notably a single-particle gap but gapless spin and charge excitations, can in principle be understood in the framework of orthogonal metals. However, important and interesting differences arise in the present setting compared to single-particle mean-field theories and other models. We also discuss the role of the local constraints from the slave-spin representation within an extended phase diagram that includes the spatial dimension as a parameter, thereby making contact with previous work in infinite dimensions. Finally, we highlight the absence of $\pi$-flux configurations in the slave-spin formulation, in particular in the context of topologically ordered fractional phases predicted at the mean-field level.