Regensburg 2007 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 10: Superconductivity - Properties, Electronic Structure, Order Parameter

TT 10.6: Vortrag

Dienstag, 27. März 2007, 10:45–11:00, H18

First principles Thermodynamics of YBa₂Cu₃O₇ — Volker Pankoke^1,2, •Rolf Heid¹, and Klaus-Peter Bohnen¹ — ¹Forschungszentrum Karlsruhe, Institut für Festkörperphysik — ²Forschungszentrum Karlsruhe, Institut für Wissenschaftliches Rechnen

Modern density-functional based methods nowadays allow for an accurate calculation of phonon spectra and their dependence on structural parameters, which is a prerequisite for the study of finite temperature properties based on the free energy. Due to the large numerical costs, however, ab initio studies of thermodynamic properties have been restricted in most cases to crystals with simple lattice structures.

We will present an application of this ab initio approach to the cuprate superconductor YBa₂Cu₃O₇ with its rather complex crystal structure. Thermodynamical properties are calculated within the quasiharmonic approximation using phonon spectra obtained by density functional perturbation theory. We will discuss results for the anisotropic thermal expansion and specific heat in comparison with experiment to assess the accuracy of this approach.