Boundary effect on CDW: Friedel oscillations, STM image

TL;DR

This paper investigates how open boundaries influence charge density waves, revealing boundary-induced oscillations, suppression of Friedel oscillations, and boundary effects observable in STM images, including asymmetries and spectral weight transfer.

Contribution

It provides a detailed analysis of boundary effects on CDW, including oscillation behavior and STM features, which were not thoroughly characterized before.

Findings

Friedel oscillations persist beyond the CDW coherence length but are suppressed in amplitude.

Boundary conditions induce asymmetry in local tunneling conductance with respect to Fermi energy.

STM images show boundary-specific features like additional zeros and spectral weight transfer.

Abstract

We study the effect of open boundary condition on charge density waves (CDW). The electron density oscillates rapidly close to the boundary, and additional non-oscillating terms (~ln(r)) appear. The Friedel oscillations survive beyond the CDW coherence length (v_F/Delta), but their amplitude gets heavily suppressed. The scanning tunneling microscopy image (STM) of CDW shows clear features of the boundary. The local tunneling conductance becomes asymmetric with respect to the Fermi energy, and considerable amount of spectral weight is transferred to the lower gap edge. Also it exhibits additional zeros reflecting the influence of the boundary.