6 September 2000 Andreev reflection and superconducting bound states in high-Tc junctions
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Midgap states (MGS) exist at the Fermi level at surfaces and interfaces of d-wave superconductors for order parameter orientations such that a sign change of Andreev reflection can add a (pi) -shift in the Bohr-Sommerfeld quantization condition. MGS are basically robust features, but the detailed density of states, manifested e.g. in zero bias conductance peaks (ZBCP), is in principle a sensitive probe of junctions and interfaces, providing information about normal regions with suppressed order parameter, non-specular scattering from rough or disordered interfaces, impurity states, lifetimes, etc. Resonance coupling of MGS in d45/d+/- 45 SNINS junctions gives rise to large equilibrium Josephson critical current varies direct as (root)D, where D is the normal transparency of the junction. Spontaneous time-reversal symmetry breaking (TRSB) in d0/d45 junctions at low temperatures kBT << D(Delta) 0 is driven by a gain in Josephson energy for transparencies D >> (epsilon) 0/(lambda) .
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Goran P. Wendin, Goran P. Wendin, Tomas Loefwander, Tomas Loefwander, Vitaly S. Shumeiko, Vitaly S. Shumeiko, } "Andreev reflection and superconducting bound states in high-Tc junctions", Proc. SPIE 4058, Superconducting and Related Oxides: Physics and Nanoengineering IV, (6 September 2000); doi: 10.1117/12.397840; https://doi.org/10.1117/12.397840

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