Feynman diagrams versus Fermi-gas Feynman emulator

Kris van Houcke (1, 2) , Felix Werner (2, 3) , Evgeny Kozik (4) , Nikolay Prokofev (2) , Boris Svistunov (2) , Mark Ku (5) , Ariel Sommer (5) , Lawrence Cheuk (5) , Andre Schirotzek (6) , Martin Zwierlein (5)

1 UGENT - Universiteit Gent = Ghent University
2 UMass Amherst - University of Massachusetts [Amherst]
3 LKB (Lhomond) - Laboratoire Kastler Brossel
4 CPHT - Centre de Physique Théorique [Palaiseau]
5 MIT - Massachusetts Institute of Technology
6 ALS - Advanced Light Source [LBNL Berkeley]

Precise understanding of strongly interacting fermions, from electrons in modern materials to nuclear matter, presents a major goal in modern physics. However, the theoretical description of interacting Fermi systems is usually plagued by the intricate quantum statistics at play. Here we present a cross-validation between a new theoretical approach, Bold Diagrammatic Monte Carlo (BDMC), and precision experiments on ultra-cold atoms. Specifically, we compute and measure with unprecedented accuracy the normal-state equation of state of the unitary gas, a prototypical example of a strongly correlated fermionic system. Excellent agreement demonstrates that a series of Feynman diagrams can be controllably resummed in a non-perturbative regime using BDMC. This opens the door to the solution of some of the most challenging problems across many areas of physics.

Mots clés: unitary gas; BEC-BCS crossover; Diagrammatic Monte Carlo; strongly correlated fermions

Domaines: Autre [cond-mat.other]; Gaz Quantiques [cond-mat.quant-gas]

Kris van Houcke, Felix Werner, Evgeny Kozik, Nikolay Prokofev, Boris Svistunov, et al.. Feynman diagrams versus Fermi-gas Feynman emulator. Nature Physics, 2012, 8, pp.366. ⟨10.1038/NPHYS2273⟩. ⟨hal-00721961⟩