Jukka Vayrynen, Microsoft Station Q, Santa Barbara , Signatures of topological ground state degeneracy in Majorana islands

Date: Mon. January 27th, 2020, 12:45 pm-1:45 pm
Location: Rockefeller 221 (Les Foldy Room)
Website: https://scholar.google.com/citations?user=22eBkAsAAAAJ&hl=en

Title: Signatures of topological ground state degeneracy in Majorana islands

Abstract:

We consider a mesoscopic superconducting island hosting multiple pairs of Majorana zero-energy modes. The Majorana island consists of multiple p-wave wires connected together by a trivial (s-wave) superconducting backbone and is characterized by an overall charging energy $E_C$; the wires are coupled to normal-metal leads via tunnel junctions. Using a combination of analytical and numerical techniques we calculate the average charge on the island as well as non-local conductance matrix as a function of a p-wave pairing gap $\Delta_P$, charging energy $E_C$ and dimensionless junction conductances $g_i$. We find that the presence of a topological ground-state degeneracy in the island dramatically enhances charge fluctuations and leads to the suppression of Coulomb blockade effects. Specifically, in contrast with conventional (s-wave) mesoscopic superconducting islands, we find that Coulomb blockade effects are suppressed in Majorana islands regardless of the ratio $E_C/\Delta_P$ or the magnitude of the conductances $g_i$. We also discuss our findings in relation to the so-called topological Kondo effect.

 

Host: Xuan Gao