Rostock 2019 – scientific programme
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MO: Fachverband Molekülphysik
MO 24: Large and Reactive Systems
MO 24.8: Talk
Friday, March 15, 2019, 12:15–12:30, S HS 002 Biologie
Diagrammatic Monte Carlo approach to angular momentum in quantum many-body systems — •Giacomo Bighin1, Timur Tscherbul2, and Mikhail Lemeshko1 — 1IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400 Klosterneuburg, Austria — 2Department of Physics, University of Nevada, Reno, NV, 89557, USA
We introduce a Diagrammatic Monte Carlo (DiagMC) approach to molecular impurities, possessing rotational degrees of freedom [1]. The technique is based on a diagrammatic expansion [2] that merges the usual Feynman diagrams with the angular momentum diagrams known from atomic and nuclear structure theory, thereby incorporating the non-Abelian algebra inherent to quantum rotations. Due to the peculiar way in which angular momenta couple, the configuration space is larger with respect to most DiagMC applications, and a new class of updates is needed in order to span it completely.
We exemplify the technique by obtaining an all-coupling solution of the angulon model - essentially a molecular impurity in a quantum many-body environment - showing that our approach correctly recovers the strong-coupling limit. However, the technique is general and can be applied to a broad variety of systems possessing angular momentum degrees of freedom, thereby establishing a far-reaching connection between DiagMC techniques and molecular simulations.
[1] G. Bighin, T. V. Tscherbul, and M. Lemeshko, Phys. Rev. Lett. 121, 165301 (2018). [2] G. Bighin and M. Lemeshko, Phys. Rev. B 96, 419 (2017).