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Author: | Kuopanportti, Pekko |
Title: | Creation and Properties of Multiply Quantized Vortices in Dilute Bose-Einstein Condensates |
Monikvantittuneiden virtauspyörteiden luonti ja ominaisuudet harvoissa Bosen-Einsteinin kondensaateissa | |
Publication type: | Master's thesis |
Publication year: | 2008 |
Pages: | 86 Language: eng |
Department/School: | Teknillisen fysiikan laitos |
Main subject: | Materiaalifysiikka (Tfy-44) |
Supervisor: | Nieminen, Risto |
Instructor: | Möttönen, Mikko |
OEVS: | Electronic archive copy is available via Aalto Thesis Database.
Instructions Reading digital theses in the closed network of the Aalto University Harald Herlin Learning CentreIn the closed network of Learning Centre you can read digital and digitized theses not available in the open network. The Learning Centre contact details and opening hours: https://learningcentre.aalto.fi/en/harald-herlin-learning-centre/ You can read theses on the Learning Centre customer computers, which are available on all floors.
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Location: | P1 Ark TF80 | Archive |
Keywords: | Bose-Einstein condensation dilute atomic gas vortex Bosen-Einsteinin kondensaatio harva atomikaasu virtauspyörre |
Abstract (eng): | Bose-Einstein condensation of dilute ultracold alkali atom gases was achieved in 1995, and since then, these highly controllable macroscopic quantum systems have attracted wide interest. The dilute condensates provide a rare opportunity to model interacting many-body systems exhaustively and accurately from first- principles quantum field theories. One of the main signatures of Bose-Einstein condensation is superfluidity: particle currents can flow without dissipation and viscosity. The superfluidity of the condensates is intimately related to the existence and stability of topological phase singularities called quantized vortices. The trapped alkali atom gases can be either spin-polarized, or they may support different coexisting spin orientations. In this Master's Thesis, we investigate multiply quantized vortices in both scalar and spinor condensates in the zero-temperature limit. We study computationally the core size and dynamic instability of multiquantum vortices in axisymmetric scalar condensates. We also investigate the splitting mechanisms of such vortices into singly quantized ones. Furthermore, we study topological phase imprinting methods that can be used to create multiply quantized vortices in spinor condensates. Our numerical studies showed that the dynamic instability of a multiply quantized vortex increases only slightly as a function of the quantum number. It was found that the splitting of multiquantum vortices results in the formation of vortex sheets and large vortex-free domains in the condensates. We also demonstrated that vortices with odd quantum numbers can be topologically created in spinor condensates through a cyclic control of external magnetic fields. |
Abstract (fin): | Bosen-Einsteinin kondensaatio toteutettiin kokeellisesti alkalimetalliatomien muodostamissa harvoissa kaasuissa vuonna 1995, minka jalkeen nama tarkasti kontrolloitavissa olevat kvanttisysteemit ovat herattaneet runsasta mielenkiintoa. Bosen-Einsteinin kondensaatit tarjoavat ainutlaatuisen tilaisuuden vuorovaikuttavan monihiukkassysteemin tarkkaan mallintamiseen perusteorioihin nojaten. Eras kondensaatin erityispiirre on suprajuoksevuus: hiukkasten virtauksessa ei esiinny energiahavioita eika viskositeettia. Kondensaattien suprajuoksevuus liittyy laheisesti kvantittuneiden virtauspyorteiden eli vorteksien esiintymiseen jastabiilisuusominaisuuksiin. Alkalimetalliatomien muodostamat kondensaatit voivat olla joko spin-polarisoituneita tai koostua useista eri spin-tiloista. Taman diplomityon tutkimuskohteena ovat monikvantittuneet virtauspyorteet seka skalaari- etta spinorikondensaateissa. Tallaisten vorteksien kokoa ja stabiilisuusominaisuuk- sia tarkastellaan laskennallisesti skalaarikondensaateissa. Tyossa tutkitaan myos monikvanttivorteksien jakaantumista yksikvanttivortekseiksi. Lisaksi tarkastellaan topologisia menetelmia, joiden avulla monikvanttivortekseja voidaan luoda spinorikondensaatteihin. Tyossa suoritettujen numeeristen laskujen perusteella havaittiin, etta monikvanttivorteksin epastabiilisuus lisaantyy hyvin hitaasti kvanttiluvun kasvaessa. Monikvanttivorteksien jakaantumisen seurauksena kondensaatteihin syntyi seka vorteksjonoja etta suuria pyorteettomia alueita. Tyossa myos osoitettiin, etta virtauspyorteita, joiden kvanttiluku on pariton, voidaan luoda spinorikondensaatteihin ulkoisia magneettikenttia kontrolloimalla. |
ED: | 2009-02-23 |
INSSI record number: 36792
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