Regensburg 2004 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 24: Postersitzung III: Korrelierte Elektronen, ”Orbital Physics”

TT 24.4: Poster

Mittwoch, 10. März 2004, 14:30–19:00, Poster A

Quantum Monte Carlo approach to the Holstein model — •Martin Hohenadler, Hans Gerd Evertz, and Wolfgang von der Linden — Institute for Theoretical and Computational Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria

Based on the canonical Lang-Firsov transformation of the Hamiltonian, we develop a novel quantum Monte Carlo algorithm for the Holstein model with one electron. Separation of the fermionic degrees of freedom by a reweighting of the probability distribution leads to a dramatic reduction in computational effort. A principle component representation of the phonon degrees of freedom allows us to sample completely uncorrelated phonon configurations. Despite a minus-sign problem, which is a consequence of the Lang-Firsov transformation, the combination of these elements enables us to perform efficient simulations for a wide range of temperature, phonon frequency and electron-phonon coupling in one to three dimensions, and on clusters large enough to avoid significant finite-size effects. The algorithm is employed to investigate the problem of small polaron formation in the Holstein model, and comparison with exact results and with existing work is made. Moreover, the new ideas presented here can also be applied to the many-electron case.