SFB 668


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23.11.2006, 15:30
Jungiusstr. 11, Hörsaal AP

SFB 668 - Kolloquium

Dr. Philipp Werner (Columbia University, USA):

Hybridization-expansion continuous time impurity solver

One of the challenges of theoretical condensed matter physics is the accurate solution of quantum impurity models. They are important both in their own right and as a crucial ingredient in the dynamical mean field method of approximating the properties of interacting fermions on a lattice. Recently, a new class of impurity solvers has been developed, based on the stochastic evaluation of a diagrammatic expansion of the partition function and the resummation of diagrams into determinants. Two complimentary approaches are possible: a weak-coupling expansion in powers of the coupling constants or an expansion in powers of the impurity-bath mixing. I will discuss the hybridization-expansion approach in a representation which is suitable for density-density interactions and a generalization to multi-orbital models with exchange (or clusters). The important feature is that the perturbation order which is needed decreases as the interaction strength is increased. I will demonstrate that the new algorithm allows unprecedented access to the low-temperature physics for interaction strengths of the order of the critical value for the Mott transition.

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