Path integral Monte Carlo (PIMC) simulations are used to calculate the momentum distribution of the homogeneous electron gas at finite temperature. This is done by calculating the off-diagonal elements of the real-space density matrix, represented in PIMC by open paths. It is demonstrated how the restricted path integral Monte Carlo methods can be extended in order to deal with open paths in fermionic systems where a sign problem is present. The computed momentum distribution shows significant deviations for strong correlation from free fermion results but agrees with predictions from variational methods.
Submitted to Phys. Rev. B, October 16, 2003.