We have directly imaged the anisotropic nonlinear Meissner effect in an unconventional superconductor through the nonlinear electrodynamic response of both (bulk) gap nodes and (surface) Andreev bound states. A superconducting thin film is patterned into a compact self-resonant spiral structure, excited near resonance in the radio-frequency range, and scanned with a focused laser beam perturbation. At low temperatures, direction-dependent nonlinearities in the reactive and resistive properties of the resonator create photoresponse that maps out the directions of nodes, or of bound states associated with these nodes, on the Fermi surface of the superconductor. The method is demonstrated on the nodal superconductor YBa2Cu3O7-δ and the results are consistent with theoretical predictions for the bulk and surface contributions.
A. P. Zhuravel et al., "Imaging the Anisotropic Nonlinear Meissner Effect in Nodal YBa 2Cu3O7-δ Thin-Film Superconductors," Physical Review Letters, vol. 110, no. 8, pp. 087002-1-087002-5, American Physical Society (APS), Feb 2013.
The definitive version is available at https://doi.org/10.1103/PhysRevLett.110.087002
Keywords and Phrases
Andreev bound state; Bound state; Focused laser beams; Gap nodes; Low temperatures; Meissner effect; Nodal superconductors; Photoresponses; Radio frequencies; Spiral structures; Surface contribution; Theoretical prediction; Thin-film superconductors; Unconventional superconductors; Anisotropy; Superconductivity; Superconducting films
International Standard Serial Number (ISSN)
Article - Journal
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