English

The "normal" state of superconducting cuprates might really be normal after all

Superconductivity 2016-08-31 v1

Abstract

High magnetic field studies of cuprate superconductors revealed a non-BCS temperature dependence of the upper critical field Hc2(T)H_{c2}(T) determined resistively by several groups. These determinations caused some doubts on the grounds of both the contrasting effect of the magnetic field on the in-plane and out-of-plane resistances reported for large Bi2212 sample and the large Nernst signal \emph{well above} TcT_{c}. Here we present both ρab(B)\rho_{ab}(B) and ρc(B)\rho_{c}(B) of tiny Bi2212 crystals in magnetic fields up to 50 Tesla. None of our measurements revealed a situation when on the field increase ρc\rho_c reaches its maximum while ρab\rho_{ab} remains very small if not zero. The resistive %upper critical fields estimated from the in-plane and out-of-plane Hc2(T)H_{c2}(T) estimated from ρab(B)\rho_{ab}(B) and ρc(B)\rho_{c}(B) are approximately the same. Our results support any theory of cuprates that describes the state above the resistive phase transition as perfectly normal with a zero off-diagonal order parameter. In particular, the anomalous Nernst effect above the resistive phase transition in high-TcT_{c} cuprates can be described quantitatively as a normal state phenomenon in a model with itinerant and localised fermions and/or charged bosons.

Keywords

Cite

@article{arxiv.cond-mat/0410075,
  title  = {The "normal" state of superconducting cuprates might really be normal after all},
  author = {V. N. Zavaritsky and A. S. Alexandrov},
  journal= {arXiv preprint arXiv:cond-mat/0410075},
  year   = {2016}
}