Fermionic physics from ab initio path integral Monte Carlo simulations of fictitious identical particlesShow others and affiliations
2023 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 159, no 16Article in journal (Refereed) Published
Abstract [en]
The ab initio path integral Monte Carlo (PIMC) method is one of the most successful methods in statistical physics, quantum chemistry and related fields, but its application to quantum degenerate Fermi systems is severely hampered by an exponential computational bottleneck: the notorious fermion sign problem. Very recently, Xiong and Xiong [J. Chem. Phys. 157, 094112 (2022)] have suggested to partially circumvent the sign problem by carrying out simulations of fictitious systems guided by an interpolating continuous variable ξ ∈ [-1, 1], with the physical Fermi- and Bose-statistics corresponding to ξ = -1 and ξ = 1. It has been proposed that information about the fermionic limit might be obtained by calculations within the bosonic sector ξ > 0 combined with an extrapolation throughout the fermionic sector ξ < 0, essentially bypassing the sign problem. Here, we show how the inclusion of the artificial parameter ξ can be interpreted as an effective penalty on the formation of permutation cycles in the PIMC simulation. We demonstrate that the proposed extrapolation method breaks down for moderate to high quantum degeneracy. Instead, the method constitutes a valuable tool for the description of large Fermi-systems of weak quantum degeneracy. This is demonstrated for electrons in a 2D harmonic trap and for the uniform electron gas (UEG), where we find excellent agreement (∼0.5%) with exact configuration PIMC results in the high-density regime while attaining a speed-up exceeding 11 orders of magnitude. Finally, we extend the idea beyond the energy and analyze the radial density distribution (2D trap), as well as the static structure factor and imaginary-time density-density correlation function (UEG).
Place, publisher, year, edition, pages
AIP Publishing , 2023. Vol. 159, no 16
National Category
Other Physics Topics Condensed Matter Physics
Identifiers
URN: urn:nbn:se:kth:diva-339511DOI: 10.1063/5.0171930ISI: 001136351100001PubMedID: 37888764Scopus ID: 2-s2.0-85175273351OAI: oai:DiVA.org:kth-339511DiVA, id: diva2:1811745
Note
QC 20231114
2023-11-142023-11-142024-02-06Bibliographically approved