2016/10/31 by Olivier Juillet, Alexandre Leprévost, Jérémy Bonnard +1
Physics and Astronomy · #Brownian motion #Cold Atom Physics and Bose-Einstein Condensates #Function (biology) #Motion (physics) #Observable #Physics of Superconductivity and Magnetism #Quantum #Quantum many-body systems #Random matrix #Space (punctuation) #Superfluidity #Wave function #cond-mat.quant-gas #cond-mat.str-el
paper · pdf · doi:10.1088/1751-8121/aa62b6
published as J. Phys. A Math. Theor. 50, 175001 (2017) · 35 pages, 2 figures, minor typos corrected
openalex created_date 2016/11/04 · openalex publication_date 2017/02/24 · arxiv created 2017/03/30 · arxiv updated 2017/03/31 · openalex updated_date 2026/08/06
Abstract The so-called phaseless quantum Monte-Carlo method currently offers one of the best performing theoretical framework to investigate interacting Fermi systems. It allows to extract an approximate ground-state wavefunction by averaging independent-particle states undergoing a Brownian motion in imaginary-time. Here, we extend the approach to a random walk in the space of Hartree–Fock–Bogoliubov (HFB) vacua that are better suited for superconducting or superfluid systems. Well-controlled statistical errors are ensured by constraining stochastic paths with the help of a trial wavefunction. It also guides the dynamics and takes the form of a linear combination of HFB ansätze. Estimates for the observables are reconstructed through an extension of Wick’s theorem to matrix elements between HFB product states. The usual combinatory complexity associated to the application of this theorem for four- and more- body operators is bypassed with a compact expression in terms of Pfaffians. The limiting case of a stochastic motion within Slater determinants but guided with HFB trial wavefunctions is also considered. Finally, exploratory results for the spin-polarized Hubbard model in the attractive regime are presented.