Regensburg 1998 – wissenschaftliches Programm
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SYD: Symposium Phasenübergänge in Elektronensystemen mit Wechselwirkung
SYD 2: Phasenübergänge in Elektronensystemen mit Wechselwirkung II
SYD 2.4: Fachvortrag
Mittwoch, 25. März 1998, 18:00–18:20, H3
Strond Coupling Expansion for Quantum Systems at Finite Temperatures — •N. Elstner1 and R.R.P. Singh2 — 1Universität Bonn — 2University of California, Davis CA 95616,USA
By combining conventional finite-temperature many-body perturbation theory with cluster expansions, we develop a systematic method to carry out high order arbitrary temperature perturbative calculations numerically. The method is well suited to studying the thermodynamic properties of quantum disordered and quantum critical phases at finite temperatures. As an application, we calculate the magnetic susceptibility, internal energy and specific heat of the bilayer Heisenberg model and of dimerized spin chains. For a wide range of coupling constants these expansions show excellent convergence at all temperatures. The method is also applicable to frustrated and quenched random spin systems as well as to electronic models around the strong coupling limit.