Superconductivity in Cuprates, The Van Hove Scenario: A Review

摘要: Many recent experiments of angular resolved photoemission spectroscopy (ARPES) have confirmed the existence saddle points (van Hove singularity or v.H.s.) close to Fermi level in five different copper oxide compounds by three groups, Stanford, Argonne and Wisconsin. These observations been made following : (Bi 2212), (NCCO). establish a general feature very high superconductors cuprates van singularities are present level. This is probably not purely accidental we think that any theoretical model must take into account these experimental facts. The origin still controversial role mechanism superconductivity yet established, but want stress 2D itinerant electrons presence v.H. band structure has already explained certain number facts, i.e. anomalous isotope effect4, marginal liquid effects small values coherence length6. It was also shown middle wide circumstances, Coulomb repulsion renormalized replaced smaller number, effective electron-phonon coupling remains positive. We this fact explains low observed where narrow determined ARPES. using weakly screened interaction obtain strong gap anisotropy. then compute density states (D.O.S.) quasiparticle excitations superconducting state, frame work model. study effect doping, distance between apply result calculation tunneling characteristics electronic specific heat influence doping on screening length thus explain why themaximum when finally ofdoping, normal state properties interpret some so-called pseudogap.