No equivalence between hydrodynamic and dispersive mass of the charged polaron

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Main Authors: Myśliwy, Krzysztof, Wysocki, Piotr, Jachymski, Krzysztof
Format: Preprint
Published: 2025
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author Myśliwy, Krzysztof
Wysocki, Piotr
Jachymski, Krzysztof
author_facet Myśliwy, Krzysztof
Wysocki, Piotr
Jachymski, Krzysztof
contents We consider the problem of a charged impurity exerting a weak, slowly decaying force on its surroundings, treating the latter as an ideal compressible fluid. In the semiclassical approximation, the ion is described by the Newton equation coupled to the Euler equation for the medium. After linearization, we obtain a simple closed formula for the effective mass of the impurity, depending on the interaction potential, the mean medium density, and sound velocity. Thus, once the interaction and the equation of state of the fluid is known, an estimate of the hydrodynamic effective mass can be quickly provided. Going beyond the classical case, we show that replacing the Newton with Schrödinger equation can drastically change the behavior of the impurity. In particular, the scaling of the Fermi polaron effective mass with the medium density is opposite in quantum and classical scenario. Our results are relevant for experimental systems featuring low energy impurities in Fermi or Bose systems, such as ions immersed in neutral atomic gases.
format Preprint
id arxiv_https___arxiv_org_abs_2504_12040
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle No equivalence between hydrodynamic and dispersive mass of the charged polaron
Myśliwy, Krzysztof
Wysocki, Piotr
Jachymski, Krzysztof
Quantum Gases
Fluid Dynamics
Quantum Physics
We consider the problem of a charged impurity exerting a weak, slowly decaying force on its surroundings, treating the latter as an ideal compressible fluid. In the semiclassical approximation, the ion is described by the Newton equation coupled to the Euler equation for the medium. After linearization, we obtain a simple closed formula for the effective mass of the impurity, depending on the interaction potential, the mean medium density, and sound velocity. Thus, once the interaction and the equation of state of the fluid is known, an estimate of the hydrodynamic effective mass can be quickly provided. Going beyond the classical case, we show that replacing the Newton with Schrödinger equation can drastically change the behavior of the impurity. In particular, the scaling of the Fermi polaron effective mass with the medium density is opposite in quantum and classical scenario. Our results are relevant for experimental systems featuring low energy impurities in Fermi or Bose systems, such as ions immersed in neutral atomic gases.
title No equivalence between hydrodynamic and dispersive mass of the charged polaron
topic Quantum Gases
Fluid Dynamics
Quantum Physics
url https://arxiv.org/abs/2504.12040