# Berlin 2015 – wissenschaftliches Programm

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# TT: Fachverband Tiefe Temperaturen

## TT 71: Correlated Electrons: Poster Session

### TT 71.78: Poster

### Mittwoch, 18. März 2015, 15:00–18:00, Poster B

**Development and Application of Full Configuration Interaction Quantum Monte Carlo Techniques for Strongly Correlated Electron Lattice Models** — •Werner Dobrautz — Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany

Applications of Quantum Monte Carlo techniques to strongly correlated electron lattice models, like the Hubbard model, are severely hindered by the existence of the renowned sign problem.

In diffusion Monte Carlo methods this problem can be avoided by imposing a certain nodal structure on the emerging ground state solution. This necessary prior knowledge is not needed in the recently developed Full Configuration Interaction Monte Carlo algorithm, but emerges during a simulation due to its formulation of particle dynamics in a fully anti-symmetrized space of Slater determinants. But the ensure convergence to the correct ground state a cancellation of positive and negative weighted particles on Slater determinants during simulation has to happen. But the required amount of simulated particles heavily depends on the chosen single-particle basis functions in which the Slater determinants are constructed.

The unitary group approach to the non-relativistic electron problem allows us to efficiently formulate the FCIQMC method in the space of eigenfunctions of the spin operator S. This not only greatly decreases the Hilbert space size of the problem, but also allows us to restrict solutions to specific total spin quantum numbers.