Clarification of charge-density wave gap symmetry and topology in bulk 1T-TiSe2

Shin-Ming Huang^1*, Su-Yang Xu², Bahadur Singh^3,4, Ming-Chien Hsu¹, Chuang-Han Hsu^5,6, Chenliang Su³, Arun Bansil⁴, Hsin Lin⁷

¹Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan
²Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
³SZU-NUS Collaborative Center and International Collaborative Laboratory of 2D Materials for Optoelectronic Science & Technology, Engineering Technology Research Center for 2D Materials Information Functional Devices and Systems of Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, ShenZhen, China
⁴Department of Physics, Northeastern University, Boston, Massachusetts, USA
⁵Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore
⁶Department of Physics, National University of Singapore, Singapore
⁷Institute of Physics, Academia Sinica, Nankang, Taipei, Taiwan

* Presenter:Shin-Ming Huang, email:shinming@mail.nsysu.edu.tw

The charge density wave (CDW) in 1T-TiSe2 accompanied by the periodic lattice distortion has a nontrivial symmetry configuration. The symmetry is important as an indication of the mechanism and a cue for experimental probes. We examine the symmetry of the system and clear up the connection of electronic structures between the normal and the CDW states. Especially, we unravel the consequential irreducible representations (IRs) of electronic states and, more ahead, those of gap functions among bands when the CDW occurs. Normally symmetry-related topology will be achieved directly, so we assert that the theory is valuable and practical for the search of topological CDW insulators.

Keywords: charge density wave, topological insulator