Diamagnetic response of a superconducting surface superstructure: Si(111)-√7×√3-In

Abstract

Macroscopic superconductivity in various ultrathin films at the ultimate two-dimensional limit, i.e., films with thickness of only one- or two-atomic layers supported by single-crystal surfaces, has manifested itself in experiments with only zero resistance but not yet with the Meissner effect due to the lack of a proper in situ technique, although both phenomena are the defining characteristics of a superconductor. Using a self-developed multifunctional scanning tunneling microscope, we succeeded in detecting not only the macroscopic supercurrent but also diamagnetic response of a two-atomic-layer indium film on a Si(111) surface. The diamagnetic measurements reveal that the low-temperature variation of penetration depth follows the Bardeen-Cooper-Schrieffer theory in the dirty limit. The magnitude of the pair-breaking interaction is determined to be 0.80 from the magnetic field dependence of the zero-temperature penetration depth, which implies that the pairing symmetry deviates slightly from an isotropic s wave. The present work demonstrates that it is possible to observe the Meissner effect in ultrathin superconducting films that are vulnerable to air, which is very helpful for a detailed understanding of the microscopic pairing mechanism.

Source-reported materials — not catalogue approval

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