Holographic superconductors with the general RF2-type couplings

We explore the effects of the general non-minimally coupled [Formula: see text]-type couplings on the holographic s-wave superconductors numerically in the Schwarzschild-anti-de Sitter (AdS) background. We calculate the condensation and conductivity of the model for the coupling parameters a1 and [Formula: see text]. We obtain that the bigger deviations of the parameter a1 from the minimal case lead to the larger deviations of the gap frequency from the universal value [Formula: see text]. Moreover, the smaller [Formula: see text] and a1 cause to gradually stronger and narrower coherence peak.

TUNNELING STUDY ON Ba2Ca3Cu4O8(O1-xFx)2

We report the tunneling conductance on a quadruple-layered cuprate, Ba 2 Ca 3 Cu 4 O 8( O 1-x F x)2 (2x~1.4, Tc~100 K ) that includes inequivalent outer (OP) and inner (IP) CuO 2 planes in a unit cell. Typical tunneling conductance displays the spectral dip structures as well as the superconducting gap (SCG) with clear coherence peaks. However we sometimes observe a pseudogap (PG) like structure without coherence peak at 4.2K. The magnitude of PG at 4.2K is larger than that of SCG at 4.2K and its conductance curve displays a faint structure at low energy. Therefore its origin would be different from that of small-PG observed at above Tc. In addition, we find that there are two kinds of SCGs that originate from IP and OP, and this result suggests that the superconducting property at IP is different from that at OP because of the imbalance of doped carrier between IP and OP. The observation of large PG at low temperature suggests the existence of some form of hidden ordered state at T<Tc and it would coexist with superconductivity.