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Dark continuum in the spectral function of the resonant Fermi polaron

Olga Goulko, University of Massachussets Amherst

18.12.2015 at 09:00 

The Fermi polaron is an impurity interacting with a sea of fermions. It is an exemplary system to study impurity problems, strongly imbalanced Fermi gases and quasiparticles. Experiments probe its spectral function, which is directly linked to many physical properties. I will describe the first numerical results for the polaron spectral function with controlled error bars, obtained with diagrammatic Monte Carlo and analytic continuation. The spectral function exhibits a narrow ground state peak and another broad peak at positive energy, which are separated by a region of extremely low spectral weight. This "dark continuum" surprisingly starts to emerge in the absence a small interaction-related parameter, and quickly broadens into a gap-like structure deeper on the BEC side. We establish a controlled upper bound on its integrated weight.

A 450, Theresienstr. 37