Local density of states and Friedel oscillations around a non-magnetic impurity in unconventional density wave

TL;DR

This paper theoretically investigates how a non-magnetic impurity affects the local density of states and Friedel oscillations in a quasi-one-dimensional unconventional density wave, revealing resonant states and power-law decay of oscillations.

Contribution

It introduces a self-consistent T-matrix approach to analyze impurity effects in unconventional density waves, highlighting unique resonance features and oscillation decay behaviors.

Findings

Resonant states appear near the Fermi level around impurities.

Friedel oscillations decay as a power law beyond the coherence length.

Impurity contributions to entropy and specific heat are quantified.

Abstract

We present a mean-field theoretical study on the effect of a single non-magnetic impurity in quasi-one dimensional unconventional density wave. The local scattering potential is treated within the self-consistent $T$-matrix approximation. The local density of states around the impurity shows the presence of resonant states in the vicinity of the Fermi level, much the same way as in $d$-density waves or unconventional superconductors. The assumption for different forward and backscattering, characteristic to quasi-one dimensional systems in general, leads to a resonance state that is double peaked in the pseudogap. The Friedel oscillations around the impurity are also explored in great detail, both within and beyond the density wave coherence length $\xi_0$. Beyond $\xi_0$ we find power law behavior as opposed to the exponential decay of conventional density wave. The entropy and specific heat contribution of the impurity are also calculated for arbitrary scattering strengths.