Current aspects of topological superconductivity
TYPESolid State Seminar
Speaker:Arbel Haim
Location:Lidow Nathan Rosen (300)

Recent  experiments have  provided mounting  evidence for the  existence of Majorana bound states (MBSs) in condensed-matter systems. Until the long-term  goal of braiding MBSs is achieved, one is  prompted  to ask: what is  the  next  step  in  the  study  of topological superconductivity and MBSs? In my talk I will discuss two topics relating to this question. In the first  part  I  will  examine  the possibility of,  not  only  detecting  the  Majoranas,  but  also  witnessing some of their exotic properties. In particular their non-local nature, or in other words, the fact that the MBS is half a fermion whose occupation is encoded in a nonlocal way. I will show that current cross  correlations in  a  T-junction  with  a  single MBS exhibit universal  features,  related  to  the Majorana nonlocality. This will be contrasted with the case of an accidental low-energy Andreev bound  state. In the second part I  will discuss the  possibility  of  realizing a  different  topological phase hosting MBSs in  currently  available experimental  platforms.  This  will  be a topological superconducting phase  which  is  protected by time-reversal symmetry, and  which is characterized by  having  a  Kramers’ pair  of  MBSs  at  each  end. As  I  will  discuss, repulsive  interactions  are  a necessary ingredient for  the  realization  of  this  phase. I  will present  a  mechanism, based  on  the interplay  between  repulsive  interactions  and  proximity  to  a  conventional  superconductor,  which drives the system into the topological phase. The effect of interactions is studied analytically using both  a  mean-field  approach  and the renormalization  group. We  corroborate  our  conclusions numerically using DMRG. [1] Arbel Haim, Anna Keselman, Erez Berg, Yuval Oreg, Phys. Rev. B, 89, 220504(R) (2014) [2] Arbel Haim, Erez Berg, Felix von Oppen, Yuval Oreg, Phys. Rev. B, 92, 245112 (2015) [3] Arbel Haim, Erez Berg, Felix von Oppen, Yuval Oreg, Phys. Rev. Lett. 114, 166406 (2015) [4] Arbel Haim, Konrad Wölms, Erez Berg, Yuval Oreg, Karsten Flensberg, Phys. Rev. B 94, 115124 (2016) [5] Arbel Haim, Erez Berg, Karsten Flensberg, Yuval Oreg, arXiv:1605.07179