Increasing superconducting $T_c$ by layering in the attractive Hubbard model

Abstract

The attractive Hubbard model has become a model readily realizable with ultracold atoms on optical lattices. However, the superconducting (superfluid) critical temperatures, $T_c$'s, are still somewhat smaller than the lowest temperatures achieved in experiments. Here we consider two possible routes, generically called layering, to increase $T_c$: a bilayer and a simple cubic lattice, both with tunable hopping, $t_z$, between attractive Hubbard planes. We have performed minus-sign--free determinant quantum Monte Carlo simulations to calculate response functions such as pairing correlation functions, uniform spin susceptibility, and double occupancy, through which we map out some physical properties. We have found that by a judicious choice of fillings and intensity of on-site attraction, a bilayer can exhibit $T_c$'s between 1.5 and 1.7 times those of the single layer; for the simple-cubic lattice the enhancement can be 30\% larger than the maximum for the single layer. We also check the accuracy of both a BCS-like estimate for $T_c$ in the attractive Hubbard model, as well as of an upper bound for $T_c$ based on the superfluid density.

12 pages, 17 figures

References in corpus (6)

• Many-Body Physics with Ultracold Gases
• Ultracold atomic gases in optical lattices: mimicking condensed matter physics and beyond
• Cooling in strongly correlated optical lattices: prospects and challenges
• Direct observation of non-local fermion pairing in an attractive Fermi-Hubbard gas
• Cooper pairing above the critical temperature in a unitary Fermi gas
• Finite temperature study of correlations in bilayer band-insulator

Cited by in corpus (2)

• Optimizing the Critical Temperature and Superfluid Density of a Metal-Superconductor Bilayer
• Observing Spatial Charge and Spin Correlations in a Strongly-Interacting Fermi Gas