## Chiral p wave superconducting order in a topological crystalline insulator

#### by Vikram Tripathi

##### at Condensed Matter Theory Seminar

Wed, 23 May 2018, 13:30

Physics building (#54) room 207

#### Abstract

Topological crystalline insulators TCIs have low energy surface states in certain high symmetry directions protected by crystalline symmetry instead of the usual time reversal symmetry The nontrivial topology is mathematically characterized by a mirror Chern number The IV VI semiconductors SnTe and related semiconducting alloys Pb 1 x Sn x Te Se were recently predicted to belong to the TCI class for a range of Pb doping Topologically protected surface states with novel electronic dispersions were found to be present on certain surfaces invariant under reflection symmetry I will show that as a result of mirror reflection symmetry one obtains four topologically protected electron bands on the 001 surface of the crystalline topological insulator Pb x Sn 1 x Te This includes two bands containing Type II van Hove singularities accessible at relatively small values of doping The diverging density of states associated with the two dimensional Van Hove singularities enhances the possibility of Fermi surface instabilities on the TCI surface brought about by weak repulsive interparticle interactions Wavefunctions corresponding to electrons in these bands have nontrivial geometric phases that effectively impart a momentum dependence to the interparticle interactions in a given band that in turn is reflected in the symmetries of the order parameters Using a renormalization group scheme we study the effect of repulsive electron interactions on the competition of different electronic phases on the 001 surface when the chemical potential is tuned to the vicinity of the Van Hove singularities Over a wide region of parameter space of repulsive interactions we show that a chiral p wave superconducting phase is favoured Implications for experiment are discussed

Created on 21-05-2018 by Bar Lev, Yevgeny (ybarlev)

Updaded on 21-05-2018 by Bar Lev, Yevgeny (ybarlev)