Special Issue "Physics of Impurities in Quantum Gases"

A special issue of Atoms (ISSN 2218-2004).

Deadline for manuscript submissions: 30 September 2021.

Special Issue Editors

Dr. Simeon Mistakidis
E-Mail Website
Guest Editor
Department of Physics, University of Hamburg, Center for Optical Quantum Technologies, Luruper Chaussee 149, 22761 Hamburg Germany
Interests: Ultracold quantum gases; Quantum impurities; Quasiparticles; Correlated nonequilibrium dynamics of atomic mixtures and transport phenomena; Impurity-impurity correlations; Entanglement between impurity atoms and bath; Nonlinear and topological excitations in multicomponent quantum systems; Spinor gases; Few-body two-component systems; Strongly correlated quantum systems; Physics of optical lattices; Quench dynamics; Driven quantum systems; Few to many-body physics
Dr. Artem Volosniev
E-Mail Website
Guest Editor
IST Austria, am Campus 1, 3400 Klosterneuburg, Austria
Interests: Ultracold quantum gases; Systems with impurities; Strongly correlated quantum systems

Special Issue Information

Dear Colleagues,

A problem of a mobile impurity in a quantum many-body environment is often reduced to an effective one-body model. This reduction is connected to the concept of a quasiparticle such as a polaron. The quasiparticles enjoy exciting physics that go beyond a minor change of the corresponding bare impurities. The underlying dressing mechanism strongly modifies single-particle properties of the impurity, such as its mass. Remarkably, it also affects impurity-impurity interactions, which usually become more attractive and might even support different types of additional bound states.

Recently, quantum systems with impurities have been realized in cold-atom experiments. These experiments offer a unique possibility to study, for instance, the spectra, the residua, and the effective mass of the generated quasiparticles, to monitor the trajectories of the impurities and even to witness induced impurity-impurity correlations. They spur a wave of theoretical works on the dynamical and static properties of quasiparticles, with particular focus on emergent correlation effects. Notable phenomena, beyond simple single-particle characteristics, include nonlinear pattern formation, induced impurity-impurity correlations, relaxation processes, and peculiar transport properties. All of the above-mentioned activities are a part of an exciting discussion that shapes our understanding of quasiparticles.

The aim of this Special Issue of Atoms is to contribute to this discussion by highlighting recent advances regarding the physics of impurities in quantum gases. The Special Issue will collect theoretical and experimental works dedicated to fundamental properties and universal aspects of quasiparticles, as well as to applications of the quasiparticle concept in different contexts such as trapped mixtures of bosons or fermions, Rydberg systems, cavity settings, etc. The Special Issue will contain studies of multicomponent setups and quantum mixtures, ranging from the many-body correlated dynamics to ground state properties of few particles, and few-body processes that play a role in many-body systems with impurities. We invite authors to submit original research as well as short pedagogical reviews and communications with technical details that can lead to a substantially improved understanding of the existing theoretical and experimental results. 

Dr. Simeon Mistakidis
Dr. Artem Volosniev
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Atoms is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Quantum gases and mixtures;
  • Systems with impurities;
  • Polarons;
  • Rydberg polarons;
  • Polaritons;
  • Induced interactions;
  • Bipolarons;
  • Pattern formation;
  • Multicomponent few-body systems;
  • Engineering of Hamiltonians (correlations);
  • Few-body scattering processes;
  • Experimental techniques in quasiparticle and few-body physics

Published Papers (3 papers)

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Research

Open AccessArticle
Initial Dynamics of Quantum Impurities in a Bose–Einstein Condensate
Atoms 2021, 9(2), 22; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms9020022 - 27 Mar 2021
Viewed by 312
Abstract
An impurity immersed in a medium constitutes a canonical scenario applicable in a wide range of fields in physics. Though our understanding has advanced significantly in the past decades, quantum impurities in a bosonic environment are still of considerable theoretical and experimental interest. [...] Read more.
An impurity immersed in a medium constitutes a canonical scenario applicable in a wide range of fields in physics. Though our understanding has advanced significantly in the past decades, quantum impurities in a bosonic environment are still of considerable theoretical and experimental interest. Here, we discuss the initial dynamics of such impurities, which was recently observed in interferometric experiments. Experimental observations from weak to unitary interactions are presented and compared to a theoretical description. In particular, the transition between two initial dynamical regimes dominated by two-body interactions is analyzed, yielding transition times in clear agreement with the theoretical prediction. Additionally, the distinct time dependence of the coherence amplitude in these regimes is obtained by extracting its power-law exponents. This benchmarks our understanding and suggests new ways of probing dynamical properties of quantum impurities. Full article
(This article belongs to the Special Issue Physics of Impurities in Quantum Gases)
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Open AccessArticle
Polaron Problems in Ultracold Atoms: Role of a Fermi Sea across Different Spatial Dimensions and Quantum Fluctuations of a Bose Medium
Atoms 2021, 9(1), 18; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms9010018 - 09 Mar 2021
Cited by 1 | Viewed by 307
Abstract
The notion of a polaron, originally introduced in the context of electrons in ionic lattices, helps us to understand how a quantum impurity behaves when being immersed in and interacting with a many-body background. We discuss the impact of the impurities on the [...] Read more.
The notion of a polaron, originally introduced in the context of electrons in ionic lattices, helps us to understand how a quantum impurity behaves when being immersed in and interacting with a many-body background. We discuss the impact of the impurities on the medium particles by considering feedback effects from polarons that can be realized in ultracold quantum gas experiments. In particular, we exemplify the modifications of the medium in the presence of either Fermi or Bose polarons. Regarding Fermi polarons we present a corresponding many-body diagrammatic approach operating at finite temperatures and discuss how mediated two- and three-body interactions are implemented within this framework. Utilizing this approach, we analyze the behavior of the spectral function of Fermi polarons at finite temperature by varying impurity-medium interactions as well as spatial dimensions from three to one. Interestingly, we reveal that the spectral function of the medium atoms could be a useful quantity for analyzing the transition/crossover from attractive polarons to molecules in three-dimensions. As for the Bose polaron, we showcase the depletion of the background Bose-Einstein condensate in the vicinity of the impurity atom. Such spatial modulations would be important for future investigations regarding the quantification of interpolaron correlations in Bose polaron problems. Full article
(This article belongs to the Special Issue Physics of Impurities in Quantum Gases)
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Open AccessArticle
Dynamics of the Creation of a Rotating Bose–Einstein Condensation by Two Photon Raman Transition Using a Laguerre–Gaussian Laser Pulse
Atoms 2021, 9(1), 14; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms9010014 - 08 Feb 2021
Viewed by 520
Abstract
We present numerical simulations to unravel the dynamics associated with the creation of a vortex in a Bose–Einstein condensate (BEC), from another nonrotating BEC using two-photon Raman transition with Gaussian (G) and Laguerre–Gaussian (LG) laser pulses. In particular, we consider BEC of Rb [...] Read more.
We present numerical simulations to unravel the dynamics associated with the creation of a vortex in a Bose–Einstein condensate (BEC), from another nonrotating BEC using two-photon Raman transition with Gaussian (G) and Laguerre–Gaussian (LG) laser pulses. In particular, we consider BEC of Rb atoms at their hyperfine ground states confined in a quasi two dimensional harmonic trap. Optical dipole potentials created by G and LG laser pulses modify the harmonic trap in such a way that density patterns of the condensates during the Raman transition process depend on the sign of the generated vortex. We investigate the role played by the Raman coupling parameter manifested through dimensionless peak Rabi frequency and intercomponent interaction on the dynamics during the population transfer process and on the final population of the rotating condensate. During the Raman transition process, the two BECs tend to have larger overlap with each other for stronger intercomponent interaction strength. Full article
(This article belongs to the Special Issue Physics of Impurities in Quantum Gases)
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