PSEUDO GAP, RESONANT-TUNNELING AND CHARGE DYNAMICS IN CUPRATE SUPERCONDUCTORS

The pseudo gap of cuprate superconductors has often been related to a spin gap kT . As an alternative kT * explanation the Coulomb gap Delt a U of blocking layer intermediate state tunneling is proposed, kT * congruent to Delta U is presented as a function of doping and block ing layer width by the counteraction of overlap and charging energies with the tunnel barrier height phi(o) congruent to 2 eV, which also de scribes quantitatively the perpendicular transport in the normal and s uperconducting state, in addition, the states at E-F of the blocking l ayer with their Delta U -values explain various spectroscopic observa tions ranging from specific heat to electron spectroscopy, like scanni ng tunneling spectroscopy (STS) and angle-resolved photoemission spect roscopy (ARPES) sampling the blocking layer. For YBCO, quasi-localized holes in the blocking layer resonant with the extended CuO2 states ar e found essential for the superconducting interaction hinting to boson ic exchanges with the blocking layer as one possible cause for the sup erconducting coherence. (C) 1998 Elsevier Science B.V. All rights rese rved.