2004/04/28 by V. N. Zavaritsky, Zavaritsky, V. N., A. S. Alexandrov +1
Chemistry · Engineering · Physics and Astronomy · #Inorganic Fluorides and Related Compounds #Physics of Superconductivity and Magnetism #Superconducting Materials and Applications #cond-mat.supr-con
paper · pdf · doi:10.48550/arxiv.cond-mat/0404678
arxiv created 2004/04/28 · arxiv updated 2009/12/01
High magnetic field studies of the cuprate superconductors revealed a non-BCS temperature dependence of the upper critical field Hc2(T) determined resistively by several groups. These determinations caused some doubts on the grounds of the contrasting effect of the magnetic field on the in-plane, ρab, and out-of-plane, ρc resistances reported for large sample of Bi2212. Here we present careful measurements of both ρab(B) and ρc(B) of tiny Bi2212 crystals in magnetic fields up to 50 Tesla. None of our measurements revealed a situation when on field increase ρc reaches its maximum while ρab remains very small if not zero. The resistive Hc2(T) estimated from ρab(B) and ρc(B) are approximately the same. We also present a simple explanation of the unusual Nernst signal in superconducting cuprates as a normal state phenomenon. Our results support any theory of cuprates, which describes the state above the resistive phase transition as perfectly 'normal' with a zero off-diagonal order parameter.