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Interface currents in topological superconductor-ferromagnet heterostructures

Speaker: 
Andreas Schnyder (Max Planck Institute, Stuttgart)
Date: 
Mon, 27/05/2013 - 12:00pm to 1:00pm
Location: 
S13-M01-11 (Physics Conference Room)
Host: 
Shaffique Adam
Event Type: 
Seminars

Abstract

Noncentrosymmetric superconductors (NCSs) are important candidates for realizing topological superconducting phases, with either a full or a nodal bulk gap. The topology of nodal phases is manifested by the presence of nondegenerate "flat-band'' zero-energy surface states, in contrast to the dispersing modes characteristic of fully gapped topological superconductors. In both cases, the edge states are expected to possess an intricate spin structure. This observation suggests that signatures of the bulk topology may be found in the magnetic response of the surface. In this talk, I demonstrate that a charge current develops in an NCS close to its interface with a ferromagnet (FM). The current is dominated by the response of the topologically protected edge states of the NCS to the FM's exchange field, and hence has completely different characteristics for the fully gapped and nodal NCS. For example, while the current in the fully gapped NCS is weak and saturates to its zero-temperature value, the presence of nondegenerate flat bands in the nodal NCS is responsible for an enormous enhancement of the current at low temperatures. This provides a novel test of the topology of NCSs, in particular of the existence of nondegenerate flat-band states. More generally, we have shown the promise of exploiting the spin texture of surface states to reveal the topological properties of the bulk.

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