Topological Superconductor in Quasi-One-Dimensional Tl2−xMo6Se6
Shin-Ming Huang1*, Chuang-Han Hsu2,3, Su-Yang Xu4, Chi-Cheng Lee5, Shiue-Yuan Shiau2,3, Hsin Lin2,3,6, Arun Bansil7
1Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan
2Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore, Singapore
3Department of Physics, National University of Singapore, Singapore, Singapore
4Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
5Institute for Solid State Physics, The University of Tokyo, Kashiwa, Japan
6Institute of Physics, Academia Sinica, Taipei, Taiwan
7Department of Physics, Northeastern University, Boston, Massachusetts, USA
* Presenter:Shin-Ming Huang,
The basic demand and also the main issue for most topological superconductors is spin triplet pairing. We discover that the quasi-one-dimensional molybdenum selenide compound will be a topological superconductor when considering inter-sublattice pairing even in the absence of spin-orbit coupling (SOC). As SOC is included, the superconductivity prefers equal spin pairing and selects the two-dimensional representation E2u, which in consequence probably induces nematic order for breaking the rotation symmetry. As the SOC is weak, we expect a strong magnetic field will depin the triplet d vector so as to remove the nematic order. We also test the doping effect and do not observe a noticeable change. Although the Majorana modes are not robust against the surface disorder owing to the quasi-one-dimensional structure, they can be pinned as a Kramers pair at the nematic vortex core.

Keywords: topological superconductor, nematic order, Majorana fermion, spin-orbit coupling