Emergence of triplet orbital pairing and non-Abelian states in ultracold multi-orbital optical lattices with quadratic band touching

Abstract

It is found that all the {\em singlet orbital pairing} instabilities are {\em absent} in a class of spin-polarized multi-orbital systems with quadratic band touching, which opens the way for {\em triplet orbital pairing} order. The ground states are found to be {\em non-Abelian} states with p-wave orbital pairing in checkerboard (away from 1/2 filling) and kagome (above 1/3 filling) lattices with {\em isotropic} attractive interaction which can be realized in ultracold multi-orbital optical lattices. The special property of such systems is generalized to more classes of multi-orbital systems, where the fully-gapped {\em non-Abelian} states are possibly the ground states. Those findings are helpful in achieving topological quantum computation.