Spin-nematic order induced superconductivity

Department of Physics, University of Sofia - 1164 Sofia, Bulgaria

^(a) naoum@phys.uni-sofia.bg

Received: 4 September 2019
Accepted: 27 January 2020

Abstract

We explore a spin-fermion model with fermion-spin-quadrupolar interaction. In a nematic phase, this interaction reduces to a four-fermion interaction that is the basis of superconductivity. When the coupling constant is positive the superconductivity is a p-wave with spin-parallel–paired fermions. When it is negative the superconductivity is a p-wave and fermions are spin-antiparallel paired. For a system with zero chemical potential, even a very small coupling can bind fermions into a bound state that leads to superconductivity. When the chemical potential is non-zero the system possesses quantum critical transition from the normal spin-nematic phase to the phase where superconductivity coexists with spin-nematicity. The value of the quantum critical fermion-spin-nematicity coupling constant depends on the chemical potential.