Dresden 2009 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 6: Postersession Correlated Electrons: (General) Theory, Low-Dimensional Systems, Kondo Physics, Heavy Fermions, Quantum-Critical Phenomena

TT 6.34: Poster

Montag, 23. März 2009, 13:00–16:45, P1A

Quantum Monte Carlo results on phonon softening in the two-dimensional Holstein model — •Prabuddha Chakraborty^1,2, Richard Scalettar², and Warren Pickett² — ¹Theoretical Physics III, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86135 Augsburg, Germany — ²University of California, Davis, CA 95616, USA

In this poster, we present new observations on the phonon spectral density in the two dimensional Holstein model. The numerical method we use is Determinant quantum Monte Carlo, combined with Maximum Entropy which is used to extract the real frequency spectral density of the phonons. We highlight one of our most surprising observations: the presence of a ubiquitous softening of the phonon at the center of the Brillouin zone, in direct contradiction to established results in this problem. We summarize the behaviour of the softening across a wide range of electron densities, phonon frequencies and electron-phonon interaction strengths.