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Degenerate ground state in a mesoscopic YBaCuO grain boundary Josephson junction

E. Il'ichev·M. Grajcar·R. Hlubina·R. P. J. IJsselsteijn·H. E. Hoenig·H. -G. Meyer·A. Golubov·M. H. S. Amin·A. M. Zagoskin·A. N. Omelyanchouk·M. Yu. Kupriyanov
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Abstract

We have measured the current-phase relationship (CPR) of symmetric 45 degree YBaCuO grain boundary Josephson junctions. Substantial deviations of the CPR from conventional tunnel-junction behavior have been observed: (i) The critical current exhibits, as a function of temperature T, a local minimum at a temperature T*. (ii) At T approximately equal to T*, the first harmonic of the CPR changes sign. (iii) For T<T*, the second harmonic of the CPR is comparable to the first harmonic, and (iv) the ground state of the junction becomes degenerate. The results are in good agreement with a microscopic model of Josephson junctions between d-wave superconductors.

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E. Il'ichev, M. Grajcar, R. Hlubina, R. P. J. IJsselsteijn, H. E. Hoenig, H. -G. Meyer, A. Golubov, M. H. S. Amin, A. M. Zagoskin, A. N. Omelyanchouk, M. Yu. Kupriyanov. 2001-06-05. Degenerate ground state in a mesoscopic YBaCuO grain boundary Josephson junction. https://doi.org/10.1103/physrevlett.86.5369

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