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Suppression of low-energy Andreev states by a supercurrent in YBa_2Cu_3O_7-delta

J. Ngai·P. Morales·J. Y. T. Wei
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Abstract

We report a coherence-length scale phenomenon related to how the high-Tc order parameter (OP) evolves under a directly-applied supercurrent. Scanning tunneling spectroscopy was performed on current-carrying YBa_2Cu_3O_7-delta thin-film strips at 4.2K. At current levels well below the theoretical depairing limit, the low-energy Andreev states are suppressed by the supercurrent, while the gap-like structures remain unchanged. We rule out the likelihood of various extrinsic effects, and propose instead a model based on phase fluctuations in the d-wave BTK formalism to explain the suppression. Our results suggest that a supercurrent could weaken the local phase coherence while preserving the pairing amplitude. Other possible scenarios which may cause the observed phenomenon are also discussed.

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J. Ngai, P. Morales, J. Y. T. Wei. 2005-05-28. Suppression of low-energy Andreev states by a supercurrent in YBa_2Cu_3O_7-delta. https://doi.org/10.1103/physrevb.72.054513

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