Pseudo gap, resonant tunneling and charge dynamics in cuprate superconductors

Abstract

The pseudo gap of cuprate superconductors has often been related to a spin gap kT *. As an alternative kT * explanation the Coulomb gap Δ U * of blocking layer intermediate state tunneling is proposed. kT *≅Δ U * is presented as a function of doping and blocking layer width by the counteraction of overlap and charging energies with the tunnel barrier height φ o≅2 eV, which also describes quantitatively the perpendicular transport in the normal and superconducting state. In addition, the states at E F of the blocking layer with their Δ U *-values explain various spectroscopic observations ranging from specific heat to electron spectroscopy, like scanning tunneling spectroscopy (STS) and angle-resolved photoemission spectroscopy (ARPES) sampling the blocking layer. For YBCO, quasi-localized holes in the blocking layer resonant with the extended CuO 2 states are found essential for the superconducting interaction hinting to bosonic exchanges with the blocking layer as one possible cause for the superconducting coherence.