Topological tunability from even-odd order parameter mixing of monolayer 1T-TiSe2 charge density wave Ming-Chien Hsu ^{1*}, Shin-Ming Huang^{1}, Bahadur Singh^{2,3}, Chuang-Han Hsu^{4,5}, Su-Yang Xu^{6}, Hsin Lin^{7}, Chenliang Su^{2}, Arun Bansil^{3}^{1}Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan^{2}SZU-NUS Collaborative Center and International Collaborative Laboratory of 2D Materials for Optoelectronic Science & Technology, Shenzhen University, Guangdong Province, China^{3}Department of Physics, Northeastern University, Massachusetts, USA^{4}Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore^{5}Department of Physics, National University of Singapore, Singapore^{6}Department of Physics, Massachusetts Institute of Technology, Massachusetts, USA^{7}Institute of Physics, Academia Sinica, Taipei, Taiwan* Presenter:Ming-Chien Hsu, email:mingchienh@gmail.com Monolayer 1T-TiSe2 has been found to have charge density wave (CDW) experimentally. The primary CDW order parameter takes the M1− symmetry having odd parity and will change parity of electronic states of the system. Due to the coexistence of three q vectors from the primary order parameter, a secondary order parameter of even parity is induced inevitably. The mixture of the two opposite-parity order parameters will break inversion symmetry, which fails connection between symmetry and topology. Here we propose a method to decouple the parity-odd and parity- even CDW gaps, so that we can perform continuously the inversion-asymmetric CDW state into an inversion-symmetric one. In this way it helps to understand topological phase transitions in inversion asymmetric systems from the inversion-symmetry point of view.
Keywords: TiSe2, charge density wave, inversion asymmetry, topological phase transition, monolayer |