Modified Method in Electronic Systems
arXiv:2105.14775 · doi:10.1103/PhysRevB.104.125137
Abstract
A modified approximation to many - body systems is developed. The approximation has the same computational complexity as the traditional approach, but uses a different truncation scheme. This scheme neglects high order connected correlation functions. A covariant (preserving Ward identities due to charge conservation) scheme for two - body correlators is employed, which holds the relation between the charge correlator and charge susceptibility. The method is tested on the two - dimensional one - band Hubbard model. Results are compared with exact diagonalization, the fluctuation - exchange (FLEX) theory and determinantal quantum Monte Carlo (DQMC) approach. The comparison for the (one - body) Green's function demonstrates that it is more precise in strong - coupling regime (especially away from half - filling) than similar - complexity approximations or FLEX. The charge correlator is in excellent agreement with the numerically exact result obtained from DQMC.
arXiv comment21 pages, 7 figures
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