Topological superconductivity induced by a Kitaev spin liquid

Abstract

We study the effective low-energy fermionic theory of the Kondo-Kitaev model to leading order in the Kondo coupling. Our main goal is to understand the nature of the superconducting instability induced in the proximate metal due to its coupling to spin fluctuations of the spin liquid. The special combination of the low-energy modes of a graphene-like metal and the form of the interaction induced by the Majorana excitations of the spin liquid furnish chiral superconducting order with $p_x + \mathrm{i} p_y$ symmetry. Computing its response to a $\mathrm{U}(1)$ gauge field moreover shows that this superconducting state is topologically non-trivial, characterized by a first Chern number of $\pm 2$.