This figure, adapted from Y. Cao et al., Nature 556, 43 (2018) (Pablo Jarillo-Herrero’s group), suggests that there might be a “ceiling” on the superconducting transition temperature of all materials.
In our paper [T. Hazra, N. Verma, and M. Randeria; Phys. Rev. X 9, 031049 (2019)] we obtained rigorous upper bounds on the superfluid density of multi-band systems with arbitrary band structure and arbitrary interactions. We thus obtained upper bounds on the superconducting Tc in 2D. For a single parabolic band we show that Tc < Ef/8 which is directly relevant for the BCS-BEC crossover in 2D Fermi gases. Using our multi-band results, we obtained useful upper bounds on the Tc for magic-angle twisted bilayer graphene.
Tuning across the BCS-BEC crossover in the multi-band superconductor Fe(SeTe): An angle-resolved photoemission study, S. Rinott et al., Science Advances 3, e1602372 (2017).
Theory of quantum oscillations in the vortex liquid state of high Tc superconductors, S. Banerjee, S. Zhang, M. Randeria; Nature Communications 4, 1700 (2013).
Projected Wavefunctions and High Tc Superconductivity in Doped Mott Insulators, M. Randeria, R. Sensarma and N. Trivedi; Invited Chapter in “The Hubbard Model: Theoretical Methods for Strongly Correlated Systems” edited by F. Mancini and A. Avella, (Springer Verlag, 2012).
The Physics Behind High-Temperature Superconducting Cuprates: The “Plain Vanilla” Version Of RVB, P. W. Anderson, P. A. Lee, M. Randeria, T. M. Rice, N. Trivedi, and F. C. Zhang; J. Phys. Cond. Mat. 16 R755-R769 (2004);