Increasing superconducting \(T_c\) by layering in the attractive Hubbard model

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...

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Bibliographic Details
Published in:arXiv.org 2024-11
Main Authors: Fontenele, Rodrigo A, Costa, Natanael C, Paiva, Thereza, dos Santos, Raimundo R
Format: Article
Language:English
Subjects:
Correlation
Cubic lattice
Fluids
Layering
Monolayers
Monte Carlo simulation
Optical lattices
Physical properties
Response functions
Superconductivity
Superfluidity
Ultracold atoms
Upper bounds
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Summary: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.
ISSN:2331-8422
DOI:10.48550/arxiv.2408.17405