Weak three-dimensional mediators of two-dimensional triplet pairing

Recent experiments demonstrate the ability to construct cold-atom mixtures with species-selective optical lattices. This allows for the possibility of a mixed-dimension system, where one fermionic atomic species is confined to a two-dimensional lattice, while another species is confined to a three-dimensional lattice that contains the two-dimensional one. We show that by tuning the density of an arbitrary number of three-dimensional atomic species, we can engineer an arbitrary, rotationally symmetric, density-density, effective interaction for the two-dimensional particles. This possibility allows for an effective interaction that favors triplet pairing for two-dimensional, SU(2) symmetric particles. Using a functional renormalization-group analysis for the two-dimensional particles, we derive and numerically confirm that the critical temperature for triplet pairing depends exponentially on the effective interaction strength. We then analyze how the stability of this phase is affected by the particle densities and the fine tuning of interaction parameters. We conclude by briefly discussing experimental considerations and the potential to study triplet-pairing physics, including Majorana fermions and spin textures, with cold atoms on optical lattices.