Diagrammatic Monte Carlo for Molecules

Electron correlations in chemical systems give rise to a wide range of interesting physical properties. Although traditional mean-field quantum chemical algorithms can reliably calculate ground state observables in many cases, finite temperature and spectral properties are only accessible with explicit inclusion of electron correlations. Diagrammatic Monte Carlo (DiagMC), which expands the physical observable in terms of connected Feynman diagrams and samples the resulting series stochastically, is a powerful technique for studying electron correlations and does not suffer from numerical sign problem which worsens with increasing system size. Recent developments in DiagMC algorithms have greatly improved their numerical efficiency. In this talk, I aim to introduce our DiagMC implementation for multi-orbital systems, and present our results when it is applied to realistic molecular systems.