Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:1811.10099 · Physical Review A

Self-localization of magnons and a magnetoroton in a binary Bose-Einstein condensate

S. V. Andreev, Oleg I. Utesov

Published Jan 21, 2020• 2 citations
arXivHTMLPDF

Abstract

We consider a two-component Bose-condensed mixture characterized by positive $s$-wave scattering lengths. We assume equal densities and intraspecies interactions. By doing the Bogoliubov transformation of an effective Hamiltonian, we obtain the lower energy magnon dispersion incorporating the superfluid entrainment between the components. We argue that $p$-wave pairing of distinct bosons should be accompanied by self-localization of magnons and formation of a magnetoroton. We demonstrate the effect on a model system of particles interacting via step potentials.

DOI
10.1103/physreva.101.013621

Related papers

Magnetoroton in a binary Bose-Einstein condensate with soft-core repuslion

S. V. Andreev, Oleg I. Utesov

We consider a two-component Bose-condensed mixture with soft-core repulsive interactions between the particles. We assume equal densities and intra-species interactions. The inter-species interaction differs both by its strength and spatial range. By doing the Bogoliubov transformation of an effective Hamiltonian we obtain the lower energy spin-wave dispersion incorporating the superfluid entrainment between the components. At sufficiently large density approaching the miscibility transition results in appearance of a roton-maxon structure in the spectrum. The roton gap may be closed by increasing the drag density, so that the phase separation occurs at a finite wavelength via self-localization of magnetorotons. This furnishes a possibility to zoom into the enigmatic interior of the Feynman vortex ring and exposes its fundamental link to the the state-of-the-art view of a roton as a ghost of the Bragg spot.

•Nov 25, 2018•0 citations

Effective interactions in a quantum Bose-Bose mixture

Oleg I. Utesov, M. I. Baglay, S. V. Andreev

We generalize the Beliaev diagrammatic theory of an interacting spinless Bose-Einstein condensate to the case of a binary mixture. We derive a set of coupled Dyson equations and find analytically the Green's functions of the system. The elementary excitation spectrum consists of two branches, one of which takes the characteristic parabolic form $\ensuremath{\omega}\ensuremath{\propto}{p}^{2}$ in the limit of a spin-independent interaction. We observe renormalization of the magnon mass and the spin-wave velocity due to the Andreev-Bashkin entrainment effect. For a three-dimensional weakly interacting gas the spectrum can be obtained by applying the Bogoliubov transformation to a second-quantized Hamiltonian in which the microscopic two-body potentials in each channel are replaced by the corresponding off-shell scattering amplitudes. The superfluid drag density can be calculated by considering a mixture of phonons and magnons interacting via the effective potentials. We show that this problem is identical to the second-order perturbative treatment of a Bose polaron. In two dimensions the drag contributes to the magnon dispersion already in the first approximation. Our consideration provides a basis for systematic study of emergent phases in quantum degenerate Bose-Bose mixtures.

arXiv:1712.00039•Physical Review A•May 23, 2018•31 citations

Magnetoroton in a two-dimensional Bose-Bose mixture

Oleg I. Utesov, S. V. Andreev

We extend our theory of slow magnons in a two-component Bose-Einstein condensate to the case of two spatial dimensions (2D). We provide a detailed discussion of polaronic corrections to the magnon branch of the elementary excitation spectrum in weakly and strongly interacting regimes. In a dilute system, the latter may be achieved by adjusting interspecies attraction so as to obtain a resonance in the $p$-wave scattering channel. Resonantly enhanced $p$-wave attraction results in the self-localization of magnons and the formation of a magnetoroton. The nature of a ground state beyond the magnetoroton instability remains to be explored. We suggest a dilute $p$-wave crystal of alternating polarization as a possible candidate. In contrast to 3D, the required strength of the attractive potential in the $s$-wave channel here corresponds to tight binding, and we suggest a potential realization of our model with excitons in 2D semiconductors.

arXiv:2404.04440•Physical review. B./Physical review. B•Jun 18, 2024•3 citations

Fermionization of a few-body Bose system immersed into a Bose-Einstein condensate

Tim Keller, Thomás Fogarty, Thomas Busch

We study the recently introduced self-pinning transition [Phys. Rev. Lett. 128, 053401 (2022)] in a quasi-one-dimensional two-component quantum gas in the case where the component immersed into the Bose-Einstein condensate has a finite intraspecies interaction strength. As a result of the matter-wave backaction, the fermionization in the limit of infinite intraspecies repulsion occurs via a first-order phase transition to the self-pinned state, which is in contrast to the asymptotic behavior in static trapping potentials. The system also exhibits an additional superfluid state for the immersed component if the interspecies interaction is able to overcome the intraspecies repulsion. We approximate the superfluid state in an analytical model and derive an expression for the phase transition line that coincides with well-known phase separation criteria in binary Bose systems. The full phase diagram of the system is mapped out numerically for the case of two and three atoms in the immersed component.

arXiv:2302.01743•SciPost Physics•Sep 14, 2023•3 citations

Spatial separation of degenerate components of magnon Bose-Einstein condensate by using a local acceleration potential

I. V. Borisenko, V. E. Demidov, Pokrovskij, V. L. +1 more

Bose-Einstein condensation (BEC) of magnons is one of few macroscopic quantum phenomena observable at room temperature. Due to competition of the exchange and the magnetic dipole interactions the minimum-energy magnon state is doubly degenerate and corresponds to two antiparallel non-zero wavevectors. Correspondingly, magnon BEC differs essentially from other condensates, since it takes place simultaneously at +/-k_min. The degeneracy of BEC and interaction between its two components have significant impact on the condensate properties. Phase locking of the two condensates causes formation of a standing wave of the condensate density and quantized vortices. Additionally, interaction between the two components is believed to be important for stabilization of the condensate with respect to the real-space collapse. Thus, the possibility to create a non-degenerate, single-component condensate is decisive for understanding of underlying physics of magnon BEC. Here, we experimentally demonstrate an approach, which allows one to accomplish this challenging task. We show that this can be achieved by using a separation of the two components of the degenerate condensate in the real space by applying a local pulsed magnetic field, which causes their motion in the opposite directions. Thus, after a certain delay, the two clouds corresponding to different components become well separated in the real space. We find that the motion of the clouds can be described well based on the peculiarities of the magnon dispersion characteristics. Additionally, we show that, during the motion, the condensate cloud harvests non-condensed magnons, which results in a partial compensation of the condensate depletion.

arXiv:2003.12436•Mar 27, 2020•0 citations

Spatial separation of degenerate components of magnon Bose–Einstein condensate by using a local acceleration potential

I. V. Borisenko, V. E. Demidov, V. L. Pokrovsky +1 more

Abstract Bose–Einstein condensation (BEC) of magnons is one of the few macroscopic quantum phenomena observable at room temperature. Due to the competition of the exchange and the magnetic dipole interactions, the minimum-energy magnon state is doubly degenerate and corresponds to two antiparallel non-zero wavevectors. Correspondingly, the room-temperature magnon BEC differs essentially from other condensates, since it takes place simultaneously at ± kmin. The degeneracy of BEC and interaction between its two components have significant impact on condensate properties. Phase locking of the two condensates causes formation of a standing wave of the condensate density and quantized vortices. Additionally, interaction between the two components is believed to be important for stabilization of the condensate with respect to a real-space collapse. Thus, the possibility to create a non-degenerate, single-component condensate is decisive for understanding of underlying physics of magnon BEC. Here, we experimentally demonstrate an approach, which allows one to accomplish this challenging task. We show that this can be achieved by using a separation of the two components of the degenerate condensate in the real space by applying a local pulsed magnetic field, which causes their motion in the opposite directions. Thus, after a certain delay, the two clouds corresponding to different components become well separated in the real space. We find that motion of the clouds can be described well based on the peculiarities of magnon dispersion characteristics. Additionally, we show that, during the motion, the condensate cloud harvests non-condensed magnons, which results in a partial compensation of condensate depletion.

Scientific Reports•Sep 10, 2020•13 citations
We consider a two-component Bose-condensed mixture characterized by positive sss-wave scattering lengths. We assume equal densities and intraspecies interactions. By doing the Bogoliubov transformation of an effective Hamiltonian, we obtain the lower energy magnon dispersion incorporating the superfluid entrainment between the components. We argue that ppp-wave pairing of distinct bosons should be accompanied by self-localization of magnons and formation of a magnetoroton. We demonstrate the effect on a model system of particles interacting via step potentials.
We consider a two-component Bose-condensed mixture with soft-core repulsive interactions between the particles. We assume equal densities and intra-species interactions. The inter-species interaction differs both by its strength and spatial range. By doing the Bogoliubov transformation of an effective Hamiltonian we obtain the lower energy spin-wave dispersion incorporating the superfluid entrainment between the components. At sufficiently large density approaching the miscibility transition results in appearance of a roton-maxon structure in the spectrum. The roton gap may be closed by increasing the drag density, so that the phase separation occurs at a finite wavelength via self-localization of magnetorotons. This furnishes a possibility to zoom into the enigmatic interior of the Feynman vortex ring and exposes its fundamental link to the the state-of-the-art view of a roton as a ghost of the Bragg spot.
We generalize the Beliaev diagrammatic theory of an interacting spinless Bose-Einstein condensate to the case of a binary mixture. We derive a set of coupled Dyson equations and find analytically the Green's functions of the system. The elementary excitation spectrum consists of two branches, one of which takes the characteristic parabolic form $\ensuremath{\omega}\ensuremath{\propto}{p}^{2}$ in the limit of a spin-independent interaction. We observe renormalization of the magnon mass and the spin-wave velocity due to the Andreev-Bashkin entrainment effect. For a three-dimensional weakly interacting gas the spectrum can be obtained by applying the Bogoliubov transformation to a second-quantized Hamiltonian in which the microscopic two-body potentials in each channel are replaced by the corresponding off-shell scattering amplitudes. The superfluid drag density can be calculated by considering a mixture of phonons and magnons interacting via the effective potentials. We show that this problem is identical to the second-order perturbative treatment of a Bose polaron. In two dimensions the drag contributes to the magnon dispersion already in the first approximation. Our consideration provides a basis for systematic study of emergent phases in quantum degenerate Bose-Bose mixtures.
We extend our theory of slow magnons in a two-component Bose-Einstein condensate to the case of two spatial dimensions (2D). We provide a detailed discussion of polaronic corrections to the magnon branch of the elementary excitation spectrum in weakly and strongly interacting regimes. In a dilute system, the latter may be achieved by adjusting interspecies attraction so as to obtain a resonance in the ppp-wave scattering channel. Resonantly enhanced ppp-wave attraction results in the self-localization of magnons and the formation of a magnetoroton. The nature of a ground state beyond the magnetoroton instability remains to be explored. We suggest a dilute ppp-wave crystal of alternating polarization as a possible candidate. In contrast to 3D, the required strength of the attractive potential in the sss-wave channel here corresponds to tight binding, and we suggest a potential realization of our model with excitons in 2D semiconductors.
We study the recently introduced self-pinning transition [Phys. Rev. Lett. 128, 053401 (2022)] in a quasi-one-dimensional two-component quantum gas in the case where the component immersed into the Bose-Einstein condensate has a finite intraspecies interaction strength. As a result of the matter-wave backaction, the fermionization in the limit of infinite intraspecies repulsion occurs via a first-order phase transition to the self-pinned state, which is in contrast to the asymptotic behavior in static trapping potentials. The system also exhibits an additional superfluid state for the immersed component if the interspecies interaction is able to overcome the intraspecies repulsion. We approximate the superfluid state in an analytical model and derive an expression for the phase transition line that coincides with well-known phase separation criteria in binary Bose systems. The full phase diagram of the system is mapped out numerically for the case of two and three atoms in the immersed component.
Bose-Einstein condensation (BEC) of magnons is one of few macroscopic quantum phenomena observable at room temperature. Due to competition of the exchange and the magnetic dipole interactions the minimum-energy magnon state is doubly degenerate and corresponds to two antiparallel non-zero wavevectors. Correspondingly, magnon BEC differs essentially from other condensates, since it takes place simultaneously at +/-k_min. The degeneracy of BEC and interaction between its two components have significant impact on the condensate properties. Phase locking of the two condensates causes formation of a standing wave of the condensate density and quantized vortices. Additionally, interaction between the two components is believed to be important for stabilization of the condensate with respect to the real-space collapse. Thus, the possibility to create a non-degenerate, single-component condensate is decisive for understanding of underlying physics of magnon BEC. Here, we experimentally demonstrate an approach, which allows one to accomplish this challenging task. We show that this can be achieved by using a separation of the two components of the degenerate condensate in the real space by applying a local pulsed magnetic field, which causes their motion in the opposite directions. Thus, after a certain delay, the two clouds corresponding to different components become well separated in the real space. We find that the motion of the clouds can be described well based on the peculiarities of the magnon dispersion characteristics. Additionally, we show that, during the motion, the condensate cloud harvests non-condensed magnons, which results in a partial compensation of the condensate depletion.
Abstract Bose–Einstein condensation (BEC) of magnons is one of the few macroscopic quantum phenomena observable at room temperature. Due to the competition of the exchange and the magnetic dipole interactions, the minimum-energy magnon state is doubly degenerate and corresponds to two antiparallel non-zero wavevectors. Correspondingly, the room-temperature magnon BEC differs essentially from other condensates, since it takes place simultaneously at ± kmin. The degeneracy of BEC and interaction between its two components have significant impact on condensate properties. Phase locking of the two condensates causes formation of a standing wave of the condensate density and quantized vortices. Additionally, interaction between the two components is believed to be important for stabilization of the condensate with respect to a real-space collapse. Thus, the possibility to create a non-degenerate, single-component condensate is decisive for understanding of underlying physics of magnon BEC. Here, we experimentally demonstrate an approach, which allows one to accomplish this challenging task. We show that this can be achieved by using a separation of the two components of the degenerate condensate in the real space by applying a local pulsed magnetic field, which causes their motion in the opposite directions. Thus, after a certain delay, the two clouds corresponding to different components become well separated in the real space. We find that motion of the clouds can be described well based on the peculiarities of magnon dispersion characteristics. Additionally, we show that, during the motion, the condensate cloud harvests non-condensed magnons, which results in a partial compensation of condensate depletion.