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Hard superconductivity of a soft metal in the quantum regime

Nature Physics volume 2, pages 173–176 (2006)Cite this article

Abstract

Superconductivity is inevitably suppressed in reduced dimensionality1,2,3,4,5,6,7,8,9. Questions of how thin superconducting wires or films can be before they lose their superconducting properties have important technological ramifications and go to the heart of understanding coherence and robustness of the superconducting state in quantum-confined geometries1,2,3,4,5,6,7,8,9. Here, we exploit quantum confinement of itinerant electrons in a soft metal, Pb, to stabilize superconductors with lateral dimensions of the order of a few millimetres and vertical dimensions of only a few atomic layers10. These extremely thin superconductors show no indication of defect- or fluctuation-driven suppression of superconductivity, and sustain supercurrents of up to 10% of the depairing current density. Their magnetic hardness implies a Bean-like critical state with strong vortex pinning that is attributed to quantum trapping of vortices. This study paints a conceptually appealing, elegant picture of a model nanoscale superconductor with calculable critical-state properties and surprisingly strong phase coherence. It indicates the intriguing possibility of exploiting robust superconductivity at the nanoscale.

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Figure 1: Equilibrium superconductive properties of ultrathin, atomically flat Pb films.
Figure 2: Scanning tunnelling microscopy images and the corresponding d.c. magnetization loops.
Figure 3: Critical current density of 7 and 9 ML thick Pb films.
Figure 4: Cole–Cole plot of real and imaginary diamagnetic susceptibility, and a plot showing current decay with time.

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Acknowledgements

We acknowledge discussions with L. Bulaevskii, A. Gurevich, V. G. Kogan, Q. Niu, and Z. Zhang. This work was funded primarily by the National Science Foundation under Contract No. DMR-0244570, and sponsored in part by the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, US Department of Energy, under contract DE-AC05-00OR22725 with Oak Ridge National Laboratory, managed and operated by UT-Battelle, LLC.

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Authors and Affiliations

  1. Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee, 37996, USA

    Mustafa M. Özer, James R. Thompson & Hanno H. Weitering

  2. Condensed Matter Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831, USA

    James R. Thompson & Hanno H. Weitering

Authors
  1. Mustafa M. Özer
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  2. James R. Thompson
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  3. Hanno H. Weitering
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Correspondence to James R. Thompson or Hanno H. Weitering.

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Özer, M., Thompson, J. & Weitering, H. Hard superconductivity of a soft metal in the quantum regime. Nature Phys 2, 173–176 (2006). https://doi.org/10.1038/nphys244

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