Random singlet-like phase of disordered Hubbard chains

TL;DR

This paper investigates disordered Hubbard chains, revealing a random singlet-like phase characterized by exponential charge decay and power-law spin correlations, using advanced numerical methods.

Contribution

It demonstrates the emergence of a random singlet-like phase in disordered Hubbard chains, a novel insight into local moment behavior in disordered insulators.

Findings

Exponential decay of charge correlations.

Power-law decay of spin correlations.

Identification of a random singlet-like phase.

Abstract

Local moment formation is ubiquitous in disordered semiconductors such as Si:P, where it is observed both in the metallic and the insulating regimes. Here, we focus on local moment behavior in disordered insulators, which arises from short-ranged, repulsive electron-electron interactions. Using density matrix renormalization group and strong-disorder renormalization group methods, we study paradigmatic models of interacting insulators: one dimensional Hubbard chains with quenched randomness. In chains with either random fermion hoppings or random chemical potentials, both at and away from half-filling, we find exponential decay of charge and fermion 2-point correlations but power-law decay of spin correlations that are indicative of the random singlet phase. The numerical results can be understood qualitatively by appealing to the large-interaction limit of the Hubbard chain, in which a remarkably simple picture emerges.