Truncated-determinant diagrammatic Monte Carlo for fermions with contact interaction

For some models of interacting fermions the known solution to the notorious sign problem in Monte Carlo (MC) simulations is to work with macroscopic fermionic determinants; the price, however, is a macroscopic scaling of the numerical effort spent on elementary local updates. We find that the ratio of two macroscopic determinants can be found with any desired accuracy by considering truncated (local in space and time) matices. In this respect, MC for interacting fermionic systems becomes similar to that for the sign-problem-free bosonic systems with system-size independent update cost. We demonstrate the utility of the truncated-determinant method by simulating the attractive Hubbard model within the MC scheme based on partially summed Feynman diagrams. We conjecture that similar approach may be useful in other implementations of the sign-free determinant schemes.

Figure 1

Energy and density dependence on the imaginary time cutoff for the Hubbard model for $L=4$. Dots represent the MC data, and solid lines are the exact diagonalization results for 10 particles (Ref. 11).

Figure 2

Potential energy dependence on the truncation radius for the Hubbard model for $L=100$.

Figure 3

(Color online) Determinant ratios $R_p^{\left(l\right)}$ as functions of $l$ for randomly selected MC configurations for the $L=100$ system.