Two-dimensional Superconductivity at a Cu-Cu₂O Interface

Superconductivity in native Cu₂O on Cu is considered for an interfacial double charge layer induced by adsorption of sub-monolayer ⁴He at temperature T ~ 4 K.  Evidence for superconductivity associated with ⁴He adsorption is found in data for the Cu work function and the shielding of patch and lattice-strain electric fields.  In the model presented for interfacial superconductivity, pairing of holes in Cu₂O is mediated by Coulomb interactions with the screening elections induced in the Cu [1].  Based on a theory for layered superconductors, the intrinsic transition temperature, T_C = βn^1/2/ζ, is determined by sheet charge density n, transverse distance between hole and electron layers ζ, and universal constant β = 1247.4(3.7) K-Ų [1].    Using parameters derived from experiment, results for T = 4.2 K are n ≃ 1.6 x10¹² cm^-2, T_C ≃ 7.9 K and Berezinskiĭ-Kosterlitz-Thouless temperature T_BKT ≃ 4.4 K.  Helium desorption causes superconductivity to vanish above T ≃ 4.8 K.

[1] D. R. Harshman and A. T. Fiory, Physica C: Supercond. Applic. 632, 1354600 (2025).