Real and Reciprocal Space Characterization of the 3-Dimensional Charge Density Wave in Quasi-1-Dimensional CuTe

TL;DR

This paper provides a comprehensive 3D characterization of charge density waves in CuTe, combining real-space imaging, momentum-resolved spectroscopy, and dynamic studies to reveal the nature and behavior of CDWs in a quasi-1D material.

Contribution

It offers the first detailed 3D analysis of CDWs in CuTe using multiple advanced techniques, confirming their inherently three-dimensional nature.

Findings

Visualization of lattice distortion via atomic force microscopy

Momentum dependence of the CDW gap in quasi-1D bands

Observation of phonon mode dynamics and gap closure during photoexcitation

Abstract

Low-dimensional materials are susceptible to electronic instabilities such as charge density waves (CDWs), originating from a divergence in the Lindhard electron response function, combined with a finite electron-phonon coupling strength. In this report, we present a detailed characterisation of the CDW in the quasi-one-dimensional material CuTe, including (1) direct visualization of lattice distortion seen with non-contact atomic force microscopy in real space, (2) the out-of-plane momentum dependency of the CDW gap size of the quasi-1-dimensional bands, by angle-resolved photoemission spectroscopy, (3) coherent dynamics of a photoexcited phonon mode seen by time- and angle-resolved photoemission spectroscopy, with frequency and wavevector q_CDW corresponding to the soft phonon modes predicted by theory. Furthermore, we find that the CDW gap closes through a transient band renormalisation. We thus confirm that, despite the quasi-1D characteristics of CuTe, it hosts inherently 3-dimensional CDWs.