Optimizing the critical temperature and superfluid density of a metal-superconductor bilayer

Abstract

A promising path to realizing higher superconducting transition temperatures Tc is the strategic engineering of artificial heterostructures. For example, quantum materials could, in principle, be coupled with other materials to produce a more robust superconducting state. In this work, we add numerical support to the hypothesis that a strongly interacting superconductor weakened by phase fluctuations can boost its Tc by hybridizing the system with a metal. Using determinant quantum Monte Carlo, we simulate a two-dimensional bilayer composed of an attractive Hubbard model and a metallic layer in two regimes of the interaction strength −|U|. In the strongly interacting regime, we find that increasing the interlayer hybridization t⊥ results in a nonmonotonic enhancement of Tc, with an optimal value comparable to the maximum Tc observed in the single-layer attractive Hubbard model, confirming trends inferred from other approaches. In the intermediate coupling regime, when −|U| is close to the value associated with the maximum Tc of the single-layer model, increasing t⊥ tends to decrease Tc, implying that the correlated layer was already optimally tuned. Importantly, we demonstrate that the mechanism behind these trends is related to enhancement in the superfluid stiffness, as was initially proposed by Kivelson [Phys. B: Condens. Matter 318, 61 (2002)].

Source-reported materials — not catalogue approval

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