Influence of Structural Defects on Charge Density Waves in 1T-TaS2

TL;DR

This study examines how various intrinsic structural defects in 1T-TaS2 influence charge density waves using advanced microscopy, spectroscopy, and theoretical calculations, revealing defect-specific electronic effects and their implications.

Contribution

It provides a detailed atomic-scale analysis of defect types in 1T-TaS2 and their distinct impacts on electronic properties, combining experimental and theoretical approaches.

Findings

Most defects are locally confined to a single CDW site.

One defect type acts as a dopant, causing band bending.

Sulfur vacancies exhibit metallic behavior and influence defect formation.

Abstract

The influence of intrinsic defects of 1T-TaS2 on charge density waves (CDW) is studied using scanning tunneling microscopy and spectroscopy (STM, STS), angle-resolved photoelectron spectroscopy (ARPES), and density functional theory (DFT). We identify several types of structural defects and find that most have a local character limited to the single CDW site, with single exception which effectively behaves as a dopant, leading to band bending and affecting multiple neighboring sites. While only one type of defect can be observed by STM topographic imaging, all defects are easily resolved by local density of states (LDOS) mapping with STS. We correlate atomically-resolved STM periodicity of defect-free 1T-TaS2 to top sulfur atoms and introduce tiling of the surface using equiangular hexagon. DFT calculations (with included Coulomb interactions) are used to investigate the electronic structure by introducing sulfur vacancy or substituting sulfur with oxygen. The sulfur vacancy is characterized by metallic properties and is identified as an origin of one of observed experimentally defects. Whereas in the case of the latter, the oxidation of 1T-TaS2 is found to result in the loss of magnetic properties expected in defect-free material.