Berlin 2018 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 15: Dual-Method Approaches to Quantum Many-Body Systems I

TT 15.1: Vortrag

Montag, 12. März 2018, 15:00–15:15, H 0104

Combining diagrammatic Monte-Carlo with large-N field theory — •Gunnar Möller — School of Physical Sciences, University of Kent, Canterbury, UK

We explore a new avenue for quantitative investigations of strongly interacting systems by combining large-N fermionic theories with stochastic sampling of high order Feynman graphs.

Our work focuses on the unitary Fermi gas as a blueprint example for a strongly interacting system of fermions without a small expansion parameter in the Hamiltonian. The unitary Fermi gas is realised experimentally in cold atomic gases of two-species fermions interacting via a Feshbach resonance [1]. Previous work has established a diagrammatic Monte-Carlo (diagMC) approach [2] but it has left uncertainties about the convergence properties of the interaction expansion [3,4]. Here, we re-examine the problem by introducing a small parameter via a large-N generalisation [5,6], to which we then apply diagMC. Formally, this yields an expansion around the mean-field superconducting theory, whose properties are recovered in the N→∞ limit. We benchmark the approach by examining density distributions and the contact parameter against prior approaches.
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