Abstract: 

Pair density wave (PDW) is a superconducting state with non-zero center-of-mass momentum Cooper pairing in the absence of external magnetic field. Recent experiments show signature of such an intriguing state. However, theoretical models supporting such a state are rare, since usual zero-momentum pairing or spin/charge order might overwhelm the PDW state. Here,  by state-of-art functional renormalization group, we show that a PDW state can be realized, out of competing orders, in a two-orbital kagome lattice under fairly realistic material conditions: finite-sized Fermi pockets and moderate local Coulomb interactions. The model enjoys the following key ingredients that make the PDW favorable: 1) The Bloch states on the Fermi surfaces are strongly sublattice and orbital polarized on the Fermi pockets, so that pairing between unequal sublattices, triggered by the correlation effect, is enforced to pick up a finite total momentum, while local onsite pairing is forbidden by the repulsive Coulomb interaction; 2) The Fermi surfaces avoid the van Hove singularities which would also enhance the particle-hole channels. The degenerage PDW states at three M-momenta on the Brillouine zone boundaries could linearly combine into chiral PDW states that are topologically nontrivial. We propose this model can be realized in some p- or d-orbital kagome materials such as CsCr₃Sb₅, and may also be simulated by cold atoms.

More details can be found in http://seminar.cpsjournals.cn/