title: Excitation gap from optimized correlation functions in quantum Monte Carlo simulations.
abstract: We give a prescription for finding optimized correlation functions for the extraction of the gap to the first excited state within quantum Monte Carlo simulations. We demonstrate that optimized correlation functions provide a more accurate reading of the gap when compared to other "nonoptimized" correlation functions and are generally characterized by considerably larger signal-to-noise ratios. We also analyze the cost of the procedure and show that it is not computationally demanding. We illustrate the effectiveness of the proposed procedure by analyzing several exemplary many-body systems of interacting spin-1/2 particles.
authors.affiliation: Department of Physics, University of California, Santa Cruz, California 95064, USA. itayhe@physics.ucsc.edu
authors.forename: Itay
authors.initials: I
authors.lastname: Hen