Regensburg 2013 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 40: Poster Session Correlated Electrons

TT 40.79: Poster

Wednesday, March 13, 2013, 15:00–19:00, Poster D

Two-particle Green functions calculated by continuous time quantum Monte Carlo simulations — •Markus Wallerberger¹, Emanuel Gull², Nico Parragh³, Giorgio Sangiovanni³, Alessandro Toschi¹, and Karsten Held¹ — ¹Technische Universität Wien, Austria — ²University of Michigan, Ann Arbor MI, USA — ³Universität Würzburg, Germany

While dynamical mean field theory (DMFT) has provided fundamental insights into the physics of strongly correlated materials, its approximations break down in low dimensional systems and near second-order phase transitions. Diagrammatic extensions of DMFT like the dynamical vertex approximation (DΓA) and the dual fermion approach which attempt to tackle this problem have the local two-particle Green function as central ingredient. Besides, this quantity is also needed for vertex corrections to response functions.

A state-of-the-art method for solving the DMFT impurity problem is the continuous-time quantum Monte Carlo (CT-QMC) method in its hybridization expansion formulation (CT-HYB). The sheer amount of information encoded in two-particle quantities, however, makes their computation very demanding in this framework. We improve on the naïve measurement by using fast Fourier transformations as well as symmetries of the Hamiltonian and of the vertex. We have implemented this method into the CT-HYB solver [1] using the Krylov method and provide benchmarks and examples for up to seven correlated orbitals.
[1] N Parragh et al., arXiv:1209.0915v1