Electronic Sound and Diffusion in Disordered Multiband Metals
Abstract
Multiband metals can host acoustic plasmons: gapless collective charge excitations involving out-of-phase motion of electrons in different bands, sometimes referred to as 'demons'. Using a hydrodynamic description valid at high temperatures, and a microscopic description with vertex corrections valid at low temperatures, we show, upon including disorder inevitably present in real materials, that the mode frequency becomes purely imaginary, resulting in diffusive behaviour over a finite range of small wave vectors $q\le q_c$. This framework provides a natural, parameter-free explanation for the anomalous nonlinear dispersion recently reported for the demon in Sr$_2$RuO$_4$, which deviates from the gapless behaviour predicted by the random phase approximation. Our results establish demons as fundamentally distinct from previously known acoustic excitations, such as phonons and photons, which exhibit inertial dynamics protected by symmetries or gauge redundancies.
Authors 4
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University of Bristol · Tyndall Centre
Affiliation as printed
School of Physics , Tyndall Avenue , Bristol , BS8 1TL , United Kingdom
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Centre National de la Recherche Scientifique · École Polytechnique · Centre de Physique Théorique · Institut Polytechnique de Paris
Affiliation as printed
CPHT , CNRS , École polytechnique , Institut Polytechnique de Paris , 91120 Palaiseau , France
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University of Geneva · Leiden University · Lorentz Center
Affiliation as printed
Department of Quantum Matter Physics , University of Geneva , CH-1211 Geneva , Switzerland
Lorentz Institute for Theoretical Physics , Leiden University , PO Box 9506 , 2300 Leiden , The Netherlands
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University of Bristol · Tyndall Centre
Affiliation as printed
School of Physics , Tyndall Avenue , Bristol , BS8 1TL , United Kingdom
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