Chirality inversion of Majorana edge modes in a Fu–Kane heterostructure

Abstract

Fu and Kane have discovered that a topological insulator with induced s -wave superconductivity (gap Δ _0 , Fermi velocity v _F , Fermi energy μ ) supports chiral Majorana modes propagating on the surface along the edge with a magnetic insulator. We show that the direction of motion of the Majorana fermions can be inverted by the counterflow of supercurrent, when the Cooper pair momentum along the boundary exceeds ${{\Delta}}_{0}^{2}/\mu {v}_{\mathrm{F}}$ . The chirality inversion is signaled by a doubling of the thermal conductance of a channel parallel to the supercurrent. Moreover, the inverted edge can transport a nonzero electrical current, carried by a Dirac mode that appears when the Majorana mode switches chirality. The chirality inversion is a unique signature of Majorana fermions in a spinful topological superconductor: it does not exist for spinless chiral p -wave pairing.

Keywords

• topological superconductors
• Majorana edge modes
• Doppler shift
• chiral edge modes
• quantum transport