Influence of structural defects on charge density waves in 1T-TaS2
Iaroslav Lutsyk, Karol Szałowski, Paweł Krukowski, P. Dąbrowski, Maciej Rogala, W. Kozłowski, Maxime Le Ster, Michał Piskorski, Dorota A. Kowalczyk, Wojciech Ryś, Rafał Dunal, Aleksandra Nadolska, Klaudia Toczek, Przemysław Przybysz, Ewa Lacinska, Johannes Binder, A. Wysmołek, Natalia Olszowska, J. Kołodziej, Martin Gmitra, Takuma Hattori, Yuji Kuwahara, Guang Bian, T.‐C. Chiang, Paweł J. Kowalczyk
Abstract
Abstract The influence of intrinsic defects of 1T-TaS 2 on charge density waves (CDWs) 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 a single CDW site, with a 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 in STS mapping. Our results indicate modulation of the Mott band gap commensurate with the CDW and breaking of the three-fold symmetry of electronic states. DFT calculations (with included Coulomb interactions) are used to investigate the electronic structure, focusing on both sulfur vacancy and oxygen-sulfur substitution. The sulfur vacancy system, characterized with a metallic behavior, is identified as the origin of one of the experimentally observed defects. Additionally, the effect of oxidation of 1T-TaS 2 depends on the substitution site, leading to the heterogeneity of electronic properties.