Non-magnetic impurities as probes of insulating and doped Mott insulators in two dimensions

TL;DR

This paper investigates how non-magnetic impurities affect two-dimensional Mott insulators, distinguishing between spinon deconfinement and confinement, and relates these properties to experimental observations upon doping.

Contribution

It introduces a method to differentiate spinon deconfinement from confinement in Mott insulators using impurity responses and finite-size spectra.

Findings

Impurity susceptibilities reveal spinon confinement or deconfinement.

Distinct spectral features differentiate the two states.

Experimental data suggest spinon confinement in certain Mott insulators.

Abstract

We characterize paramagnetic Mott insulators by their response to static, non-magnetic impurities. States with spinon deconfinement (or spin-charge separation) are distinguished from those with spinon confinement by distinct impurity susceptibilities and finite-size spectra. We discuss the evolution of physical properties upon doping to a d-wave superconductor, and argue that a number of recent experiments favor spinon confinement in the reference Mott insulating state.