Doping and thickness dependence of the commensurate charge density wave in transition metal dichalcogenides observed by Scanning tunneling microscopy

Date

Dec 7, 2017

Time

11:00 AM - 1:00 PM

Speaker

Prof. Dr. Christoph Renner

Affiliation

University of Geneva, Switzerland

Series

MPI-CPfS Festkörperphysikalisches Kolloquium

Language

en

Main Topic

Chemie

Other Topics

Physik, Chemie

Host

Dr. S. Wirth

Description

Charge density waves (CDWs) have been studied extensively over many years. However, their formation mechanism remains a puzzle and experimental evidence for the preferred mechanism of Fermi nesting is missing in a majority of actual CDW materials. CDWs are further attracting renewed interest in the context of high temperature superconductivity (HTS) – e.g. copper oxides – where suppressing the charge ordered ground state is considered a possible route to reach higher superconducting transition temperatures. I will discuss recent scanning tunneling microscopy experiments of the commensurate charge density wave as a function of doping and crystal thickness in transition metal dichalcogenides (1-3). They contribute a deeper atomic scale understanding of the CDW ground state. In CuxTiSe2, STM reveals a strong charge order deep inside the superconducting phase and clear evidence that the CDW gap is not pinned to the Fermi level. These findings question a simple competition between charge ordering and superconductivity and exclude Fermi surface nesting. STM shows that the emergence of superconductivity and the weakening of the CDW reported in bulk experiments are two distinct consequences of Cu doping. In VSe2, I will show that thickness is a true but non-trivial tuning parameter of the CDW phase transition. Collaboration with A. Scarfato, M. Spera, A. Pasztor, A. Novello, D.R. Bowler, E. Giannini 1 M. Spera et al., arXiv:1710.04096 (2017) 2 A. Pasztor et al., 2D Materials 4, 041005 (2017) 3 A. Novello et al., Physical Review Letters 118, 017002 (2017)

Links

• MPI CPfS

Last modified: Dec 7, 2017, 8:37:45 AM