C. O. Rodriguez

Superconducting and transport electron-phonon coupling constants in YBa2Cu3O7: effect of the interband anisotropy

Abstract Using previously reported first-principle frozen-phonon LDA calculations we have calculated the effective superconducting and transport electron-phonon coupling constants. We have taken into account the anisotropy due to the difference between four bands crossing the Fermi level in YBa2Cu3O7, and found that because the anisotropy influence both electron-phonon coupling constants, but in the opposite direction, the superconducting constant becomes larger than the transport one. The absolute values of the effective coupling constants is close to 2. The superconducting gaps for the different bands vary by nearly an order of magnitude. We also discuss how various experiments might have been explained in terms of the interband anisotropy.

Total Energy and Force Calculations with the LMTO Method

During the past 15 years it has become possible to perform quantum-mechanical calculations of many properties of simple materials with good accuracy using as input merely the positions of the atoms and the atomic numbers and masses. In particular, low-temperature structural properties of pure crystals and their surfaces have been obtained with astonishing accuracy through calculation of the total energy as a function of the atomic positions. Also, the Fermi surfaces of metals, the magnitude and order of magnetic moments in transition metals and many of their alloys, as well as important aspects of the electronic and atomic structures of impurities in metals and semiconductors have been accurately reproduced.1,2,3

Electronic susceptibility of YBa2Cu3O7 and its relation to phonon anomalies

A first-principles prediction of the q dependence of the electronic susceptibility of YBa2Cu3O7 and the relation to experimentally observed phonon anomalies is presented.