Berlin 2005 – wissenschaftliches Programm

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MA: Magnetismus

MA 14: Molekularer Magnetismus

MA 14.1: Vortrag

Samstag, 5. März 2005, 13:45–14:00, TU H1012

Quantum corrections for the classical density of states of Heisenberg systems — •Matthias Exler, Jochen Gemmer, and Jürgen Schnack — Universität Osnabrück, Fachbereich Physik

We present a method to add quantum corrections to the classical density of states of Heisenberg spin systems. The classical density of states is either available analytically, or we calculate it numerically using a Wang-Landau algorithm.

We use products of spin-coherent states as the source of the quantum corrections. Their energy expectation values match those of the corresponding classical spin configurations by construction. However, they are no eigenstates of the Heisenberg Hamiltonian and therefore yield energy distributions different from delta functions. We calculate moments of these spectra which can then be used to modify the classical density of states in order to get an estimate for the quantum spectrum.

We perform these calculations for different values of the spin quantum number. Therefore, we can give an impression of how the classical limit is approached with increasing spin quantum number.