title: Majorana modes at the ends of superconductor vortices in doped topological insulators.
abstract: Recent experiments have observed bulk superconductivity in doped topological insulators. Here we ask whether vortex Majorana zero modes, previously predicted to occur when s-wave superconductivity is induced on the surface of topological insulators, survive in these doped systems with metallic normal states. Assuming inversion symmetry, we find that they do but only below a critical doping. The critical doping is tied to a topological phase transition of the vortex line, at which it supports gapless excitations along its length. The critical point depends only on the vortex orientation and a suitably defined SU(2) Berry phase of the normal state Fermi surface. By calculating this phase for available band structures we determine that superconducting p-doped Bi(2)Te(3), among others, supports vortex end Majorana modes. Surprisingly, superconductors derived from topologically trivial band structures can support Majorana modes too.
authors.affiliation: Department of Physics, University of California, Berkeley, California 94720, USA.
authors.forename: Pavan
authors.initials: P
authors.lastname: Hosur
authors.forename: Pouyan
authors.initials: P
authors.lastname: Ghaemi
authors.forename: Roger S K
authors.initials: RS
authors.lastname: Mong
authors.forename: Ashvin
authors.initials: A
authors.lastname: Vishwanath