Collective excitations of a one-dimensional quantum droplet
We calculate the excitation spectrum of a one-dimensional self-bound quantum droplet in a two-component bosonic mixture described by the Gross-Pitaevskii equation (GPE) with cubic and quadratic nonlinearities. The cubic term originates from the mean-field energy of the mixture proportional to the ef...
| Autores: | , , , |
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| Tipo de recurso: | artículo |
| Fecha de publicación: | 2020 |
| País: | España |
| Institución: | Universitat Politècnica de Catalunya (UPC) |
| Repositorio: | UPCommons. Portal del coneixement obert de la UPC |
| Idioma: | inglés |
| OAI Identifier: | oai:upcommons.upc.edu:2117/328092 |
| Acceso en línea: | https://hdl.handle.net/2117/328092 https://dx.doi.org/10.1103/PhysRevA.101.051601 |
| Access Level: | acceso abierto |
| Palabra clave: | Superfluidity Bose-Einstein condensation Bose-Einstein condensates Ultracold gases Superfluïdesa Condensació de Bose-Einstein Àrees temàtiques de la UPC::Física |
| Sumario: | We calculate the excitation spectrum of a one-dimensional self-bound quantum droplet in a two-component bosonic mixture described by the Gross-Pitaevskii equation (GPE) with cubic and quadratic nonlinearities. The cubic term originates from the mean-field energy of the mixture proportional to the effective coupling constant dg, whereas the quadratic nonlinearity corresponds to the attractive beyond-mean-field contribution. The droplet properties are governed by a control parameter ¿¿dgN2/3, where N is the particle number. For large ¿>0, the droplet features the flat-top shape with the discrete part of its spectrum consisting of plane-wave Bogoliubov phonons propagating through the flat-density bulk and reflected by edges of the droplet. With decreasing ¿, these modes cross into the continuum, sequentially crossing the particle-emission threshold at specific critical values. A notable exception is the breathing mode, which we find to be always bound. The balance point ¿=0 provides implementation of a system governed by the GPE with an unusual quadratic nonlinearity. This case is characterized by the ratio of the breathing-mode frequency to the particle-emission threshold equal to 0.8904. As ¿ tends to -8, this ratio tends to 1 and the droplet transforms into the soliton solution of the integrable cubic GPE. |
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