Temperature dependence of the superconducting proximity effect quantified by scanning tunneling spectroscopy

Abstract

Here, we present the first systematic study on the temperature dependence of the extension of the superconducting proximity effect in a 1–2 atomic layer thin metallic film, surrounding a superconducting Pb island. Scanning tunneling microscopy/spectroscopy (STM/STS) measurements reveal the spatial variation of the local density of state on the film from 0.38 up to 1.8 K. In this temperature range the superconductivity of the island is almost unaffected and shows a constant gap of a 1.20 ± 0.03 meV. Using a superconducting Nb-tip a constant value of the proximity length of 17 ± 3 nm at 0.38 and 1.8 K is found. In contrast, experiments with a normal conductive W-tip indicate an apparent decrease of the proximity length with increasing temperature. This result is ascribed to the thermal broadening of the occupation of states of the tip, and it does not reflect an intrinsic temperature dependence of the proximity length. Our tunneling spectroscopy experiments shed fresh light on the fundamental issue of the temperature dependence of the proximity effect for atomic monolayers, where the intrinsic temperature dependence of the proximity effect is comparably weak.

Electrical Conductivity through a Single Atomic Step Measured with the Proximity-Induced Superconducting Pair Correlation

“…2(b)) that the DOS in the SIC layer just outside the edge of Pb islands is not uniform, which is in contrast with cases of flat metallic layers [8,11,13,14]. The site marked A, where the edge of the Pb island is directly situated on a terrace of the SIC phase, exhibits strong proximate effect, whereas at site B (C), where the edge of the island coincides with the upward (downward) step of the substrate, the proximate effect is intermediate and weak among the three sites (See Sec.…”

Scanning tunneling spectroscopy of proximity superconductivity in epitaxial multilayer graphene

“…When a superconductor is in electrical contact with a normal metal, the "leakage" of Cooper pairs via Andreev reflection causes the normal metal to acquire superconducting properties within a certain length scale from the interface. A resurgence of interest in proximity induced superconductivity has resulted from the ability to probe the superconductor-normal interface on the atomic scale with scanning tunneling spectroscopy (STS) [1][2][3][4][5][6][7]. Recent studies have probed the effects of disorder [1,5], temperature [6] and magnetic field [3], interfaces between two superconductors [4], and Josephson vortex formation [7].…”

“…A resurgence of interest in proximity induced superconductivity has resulted from the ability to probe the superconductor-normal interface on the atomic scale with scanning tunneling spectroscopy (STS) [1][2][3][4][5][6][7]. Recent studies have probed the effects of disorder [1,5], temperature [6] and magnetic field [3], interfaces between two superconductors [4], and Josephson vortex formation [7]. Only recently has proximity induced superconductivity in graphene been reported by tunneling spectroscopy in graphene films grown on Re [8].…”

General solution of 2D and 3D superconducting quasiclassical systems: coalescing vortices and nanoisland geometries

“…For instance, superconducting nanoisland systems and vortices in mesoscopic structures have received much attention experimentally. [18][19][20][21][22] These systems require not only solution in 2D or 3D, but also the description of non-trivial geometries within the numerical framework. Such solutions have been investigated using the Ginzburg-Landau formalism in the context of flux patterns and vortex states in superconductors.…”

“…Furthermore, the ability to handle complex higher dimensional geometries numerically allows for the modeling of systems which are more closely related to experiments. For instance, superconducting nanoisland systems and vortices in mesoscopic structures have received much attention experimentally 18 19 20 21 22 . These systems require not only solution in 2D or 3D, but also the description of non-trivial geometries within the numerical framework.…”