Amperian pairing at the surface of topological insulators
The surface of a 3D topological insulator is described by a helical electron state with electron’s spin and momentum locked together. I will discuss that in the presence of ferromagnetic fluctuations the surface of a topological insulator is unstable towards a superconducting state with unusual pairing dubbed as Amperian pairings. The key idea is that the dynamical fluctuations of a ferromagnetic layer deposited on the surface of a topological insulators couple to the electrons as gauge fields. The transverse components of the magnetic gauge fields are unscreened and can mediate an effective interaction between electrons. What makes the mechanism of pairing to be of Amperian type is an attractive for electrons with momenta in the same directions. We show that this attractive interaction leads to p-wave pairing instability of the Fermi surface in Cooper channel.
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