Topological supefluids from sp-orbital pairing in spin dependent lattices

Motivated by creating center-of-mass p-wave fermionic superfluids, we consider superconducting paring between s- and p-orbital fermions in optical lattices. However, due to fermi surface mismatch, it is in general energetically unfavorable for s- and p-orbital fermions to form Cooper pairs. To overcome this challenge, we propose a neat spin-dependent checkerboard lattice where s- and p-band Fermi surfaces (respectively for spin up and spin down) are almost perfectly matched leading to sp-orbital paired superfluids in the ground state. We find one type of such superfluids spontaneously breaks the time-reversal symmetry and exhibits topological characteristics featuring chiral spin currents on the edges.

Reference: Bo Liu, Xiaopeng Li, Biao Wu, W. Vincent Liu, Nature Communications 5:5064 (2014).