Physics & Astronomy Colloquium: Dr. Edwin Huang, University of Illinois, Urbana-Champaign


Location: 127 Nieuwland Science Hall

Theory of Pines' demon in multiband metals

Dr. Edwin Huang
Gordon and Betty Moore Postdoctoral Research Associate
Department of Physics and Institute for Condensed Matter Theory
University of Illinois, Urbana-Champaign

In 1956, David Pines predicted the existence of an acoustic plasmon, dubbed a "demon", in metals with multiple and sufficiently distinct charge carrier species. Despite extensive searches, demons have not been observed directly until recent momentum-resolved electron energy-loss spectroscopy (M-EELS) experiments on Sr2RuO4. Here, we discuss the theoretical conditions for the existence of demons as a stable collective excitation in multiband metals. We find, without any fitting or tuning of parameters, agreement between experimental M-EELS spectra and multi-orbital random phase approximation (RPA) calculations of the charge susceptibility. A decomposition of the calculation of the susceptibility into intra- and inter-band components provides direct evidence of the out-of-phase character of the demon. Our findings thus demonstrate the utility of numerical calculations for the microscopic interpretation of experimental spectroscopy. 

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