title: Fulde-Ferrell Superfluids without Spin Imbalance in Driven Optical Lattices.
abstract: Spin-imbalanced ultracold Fermi gases have been widely studied recently as a platform for exploring the long-sought Fulde-Ferrell-Larkin-Ovchinnikov superfluid phases, but so far conclusive evidence has not been found. Here we propose to realize an Fulde-Ferrell (FF) superfluid without spin imbalance in a three-dimensional fermionic cold atom optical lattice, where s- and p-orbital bands of the lattice are coupled by another weak moving optical lattice. Such coupling leads to a spin-independent asymmetric Fermi surface, which, together with the s-wave scattering interaction between two spins, yields an FF type of superfluid pairing. Unlike traditional schemes, our proposal does not rely on the spin imbalance (or an equivalent Zeeman field) to induce the Fermi surface mismatch and provides a completely new route for realizing FF superfluids.
authors.affiliation: Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080, USA.|Key Laboratory of Quantum Information, and Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Zheng
authors.affiliation: Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080, USA.
authors.forename: Chunlei
authors.initials: C
authors.lastname: Qu
authors.affiliation: Key Laboratory of Quantum Information, and Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.
authors.forename: Xubo
authors.initials: X
authors.lastname: Zou
authors.affiliation: Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080, USA.
authors.forename: Chuanwei
authors.initials: C
authors.lastname: Zhang