Symmetries of Strongly Correlated Electrons

V. E. Korepin, Fabian H. L. Eßler

Xiaotian Zhang

Enrico Arrigoni

B. Rosenstein, Dingping Li, Tianxing Ma +1 more

Mean field approach, although a generally reliable tool that captures major short-range correlations, often fails in symmetric low dimensional strongly correlated electronic systems like those described by the Hubbard model. In these situations a symmetry is almost broken. The problem is linked to the restoration of the symmetry due to strong fluctuations (both quantum and thermal) on all scales. The restoration of symmetry in statistical models of scalar order parameter fields was treated recently successfully on the Gaussian approximation level by symmetrization of the correlators. Here the idea is extended to fermionic systems in which the order parameter is composite. Furthermore, the precision of the correlators can be improved perturbatively. Such a scheme (based on covariant Gaussian approximation) is demonstrated on the one dimensional (1D) and 2D one band Hubbard models by comparison of the correlator with exact diagonalization and MC simulations, respectively.

Lorenzo Del Re, A. Toschi

While it is commonly assumed that correlation effects in quantum materials get partly mitigated by the onset of magnetic order, the precise role played by strong correlations in spontaneous symmetry-broken phases remains largely unexplored. Here, the authors' generalization of one of the most used diagrammatic extensions of dynamical mean-field theory to treat magnetic ordered phases provides a powerful tool to unveil the spectroscopic signatures of electronic correlations in strongly correlated quantum magnets, as highlighted by preliminary results for testbed cases.

Tobias G. W. Verhulst