Random singlet-like phase of disordered Hubbard chains

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.

Automated summary

Local moment formation is observed in disordered semiconductors, and it arises from short-ranged, repulsive electron-electron interactions. In this study, paradigmatic models of interacting insulators are used to investigate the behavior of local moments. The results show exponential decay of charge and fermion correlations, while spin correlations exhibit power-law decay, indicating the presence of a random singlet phase.