title: Helical Majorana fermions in d(x2-y2) + id(xy)-wave topological superconductivity of doped correlated quantum spin Hall insulators.
abstract: There has been growing interest in searching for exotic self-conjugate, charge-neutral low-energy fermionic quasi-particles, known as Majorana fermions (MFs) in solid state systems. Their signatures have been proposed and potentially observed at edges of topological superconcuctors with non-trivial topological invariant in the bulk electronic band structure. Much effort have been focused on realizing MFs in odd-parity superconductors made of strong spin-orbit coupled materials in proximity to conventional superconductors. In this paper, we propose a novel mechanism for realizing MFs in 2D spin-singlet topological superconducting state induced by doping a correlated quantum spin Hall (Kane-Mele) insulator. Via a renormalized mean-field approach, the system is found to exhibits time-reversal symmetry (TRS) breaking d(x2-y2) + id(xy)-wave (chiral d-wave) superconductivity near half-filling in the limit of large on-site repulsion. Surprisingly, however, at large spin-orbit coupling, the system undergoes a topological phase transition and enter into a new topological phase protected by a pseudo-spin Chern number, which can be viewed as a persistent extension of the quantum spin Hall phase upon doping. From bulk-edge correspondence, this phase is featured by the presence of two pairs of counter-propagating helical Majorana modes per edge, instead of two chiral propagating edge modes in the d + id' superconductors.
authors.affiliation: Department of Applied Physics, National University of Kaohsiung, Kaohsiung, Taiwan, R.O.C.
authors.forename: Shih-Jye
authors.initials: SJ
authors.lastname: Sun
authors.affiliation: Electrophysics Department, National Chiao-Tung University, HsinChu, Taiwan, 300, R.O.C.|Physics Division, National Center for Theoretical Sciences, HsinChu, Taiwan, 300 R.O.C.
authors.forename: Chung-Hou
authors.initials: CH
authors.lastname: Chung
authors.affiliation: Electrophysics Department, National Chiao-Tung University, HsinChu, Taiwan, 300, R.O.C.
authors.forename: Yung-Yeh
authors.initials: YY
authors.lastname: Chang
authors.affiliation: Department of Physics, National Sun Yat-Sen University, Kaohsiung, Taiwan, R.O.C.
authors.forename: Wei-Feng
authors.initials: WF
authors.lastname: Tsai
authors.affiliation: Department of Physics, Zhejiang University, Hangzhou, China.|Collaborative Innovation Center of Advanced Microstructures, Nanjing, China.
authors.forename: Fu-Chun
authors.initials: FC
authors.lastname: Zhang