Observation of mesoscopic conductance fluctuations in YBaCuO grain   boundary Josephson Junctions
  Magneto-fluctuations of the normal resistance R_N have been reproducibly observed in high critical temp erature superconductor (HTS) grain boundary junctions, at low temperatures. We attribute them to mesoscopic transport in narrow channels across the grain boundary line. The Thouless energy appears to be the relevant energy scale. Our findings have significant implications on quasiparticle relaxation and coherent transport in HTS grain boundaries. 
A. Tagliacozzo, D. Born, D. Stornaiuolo, E. Gambale, D. Dalena, F.   Lombardi, A. Barone, B. L. Altshuler and F. Tafuri