Local density of states of 1D Mott insulators and CDW states with a boundary

TL;DR

This paper analyzes the local density of states in 1D Mott insulators and CDW states with a boundary, revealing impurity pinning effects, dispersing features, and impurity-bound states relevant for STM experiments.

Contribution

It provides a detailed theoretical study of LDOS in 1D Mott insulators and CDW states with boundaries, including impurity effects and magnetic field influences.

Findings

CDW gets pinned at impurity, causing a Fourier singularity at 2k_F

Dispersing features observed above the spin gap related to spin and charge

Impurity magnetic field induces localized bound states

Abstract

We determine the local density of states (LDOS) of one-dimensional incommensurate charge density wave (CDW) states in the presence of a strong impurity potential, which is modeled by a boundary. We find that the CDW gets pinned at the impurity, which results in a singularity in the Fourier transform of the LDOS at momentum 2k_F. At energies above the spin gap we observe dispersing features associated with the spin and charge degrees of freedom respectively. In the presence of an impurity magnetic field we observe the formation of a bound state localized at the impurity. All of our results carry over to the case of one dimensional Mott insulators by exchanging the roles of spin and charge degrees of freedom. We discuss the implications of our result for scanning tunneling microscopy experiments on spin-gap systems such as two-leg ladder cuprates and 1D Mott insulators.