Berlin 2018 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 91: Correlated Electrons: Method Development

TT 91.10: Talk

Thursday, March 15, 2018, 17:30–17:45, H 0104

Having Monte Carlo decide which part of the weight to calculate: eigenstates-sampling in CTQMC — •Alexander Kowalski¹, Andreas Hausoel¹, Patrik Gunacker², and Giorgio Sangiovanni¹ — ¹Institute for Theoretical Physics and Astrophysics, University of Würzburg, Am Hubland, 97074 Würzburg, Germany — ²Institute for Solid State Physics, TU Wien, 1040 Vienna, Austria

Continuous-time quantum Monte Carlo algorithms are numerically exact methods for the solution of the Anderson impurity model often employed in DMFT calculations for strongly correlated electron systems. In the hybridization expansion CT-QMC algorithm, the local part of the system is solved exactly, which usually takes up most of the calculation time due to the exponential scaling of the local Hilbert space with the number of orbitals. A commonly used improvement is the use of conserved quantities to block-diagonalize the local Hamiltonian. We investigated the possibility of additionally sampling outer states separately in the Monte Carlo simulation, either grouped by the blocks of the Hamiltonian or individually.

We describe the details of the new Monte Carlo procedure, such as the modified updates we use to ensure ergodic and efficient sampling, as well as the influence on the average sign.

Using our implementation, we performed multi-orbital calculations at low temperatures and discuss the performance of the new method compared to conventional sampling.