Emergent Edge Modes in Shifted Quasi-One-Dimensional Charge Density Waves

TL;DR

This paper introduces a 2D phase of shifted charge density waves constructed from coupled 1D wires, revealing topological edge modes with unique spectral flow properties, stable against inter-wire coupling, and experimentally testable.

Contribution

It presents a novel 2D topological phase of shifted CDWs with edge modes exhibiting spectral pseudo-flow, expanding understanding of topological phenomena in quasi-1D systems.

Findings

Identifies topological edge modes with spectral pseudo-flow in shifted CDWs.

Shows stability of edge modes against inter-wire coupling.

Suggests experimental realization in Ta$_2$Se$_8$I.

Abstract

We propose and study a two-dimensional (2D) phase of shifted charge density waves (CDW), which is constructed from an array of weakly coupled 1D CDW wires whose phases shift from one wire to the next. We show that the fully gapped bulk CDW has topological properties, characterized by a nonzero Chern number, that imply edge modes within the bulk gap. Remarkably, these edge modes exhibit spectral pseudo-flow as a function of \emph{position} along the edge, and are thus dual to the chiral edge modes of Chern insulators with their spectral flow in \emph{momentum} space. Furthermore, we show that the CDW edge modes are stable against inter-wire coupling. Our predictions can be tested experimentally in quasi-1D CDW compounds such as Ta$_2$Se$_8$I.