Eur. Phys. J. B (2018) 91: 198
https://doi.org/10.1140/epjb/e2018-90345-8

Regular Article

Competing effects of Hund’s splitting and symmetry-breaking perturbations on electronic order in Pb_1−xSn_xTe^★

Department of Theoretical Physics, Tata Institute of Fundamental Research, Homi Bhabha Road, Navy Nagar, Colaba, Mumbai 400005, India

^a e-mail: sarbajaya@theory.tifr.res.in

Received: 28 May 2018
Published online: 12 September 2018

Abstract

We study the effect of a uniform external magnetization on p-wave superconductivity on the (001) surface of the crystalline topological insulator (TCI) Pb_1−xSn_xTe. It was shown by us in an earlier work that a chiral p-wave finite-momentum pairing (FFLO) state can be stabilized in this system in the presence of weak repulsive interparticle interactions. In particular, the superconducting instability is very sensitive to the Hund’s interaction in the multiorbital TCI, and no instabilities are found to be possible for the “wrong” sign of the Hund’s splitting. Here we show that for a finite Hund’s splitting of interactions, a significant value of the external magnetization is needed to degrade the surface superconductivity, while in the absence of the Hund’s interaction, an arbitrarily small external magnetization can destroy the superconductivity. This implies that multiorbital effects in this system play an important role in stabilizing electronic order on the surface.