Fractionalized topological d+id superconductivity in the Yao-Lee-Kondo model

Abstract

A conclusive experimental realization of 2D chiral topological superconductivity remains elusive. Here we present a theoretical demonstration that a topological $d+id$ fractionalized superconducting phase (SC*) can emerge in the weak-coupling limit of a Kondo lattice model, where conduction electrons interact with a Yao-Lee spin liquid on the honeycomb lattice (the Yao-Lee-Kondo model). Using a renormalization-group analysis, we show that exchanging Majorana spinons from the Yao-Lee spin liquid generates effective interactions among the conduction electrons and drives a Cooper instability even for arbitrarily weak Kondo coupling. We further find that the induced leading inter-orbital antiferromagnetic interaction selects topological $d+id$ spin-singlet pairing with Chern number $C=\pm 2$. Meanwhile, the Majorana fermions in the Yao-Lee spin liquid remain gapless and deconfined in this regime, so the resulting state is a fractionalized topological $d+id$ superconductor (SC*). For sufficiently strong Kondo coupling, the system instead enters a heavy Fermi liquid phase with fractionalization (HFL*).