Creation and dynamics of topological structures in Bose–Einstein condensates

Tuomas Ollikainen

Creation and dynamics of topological structures in Bose–Einstein condensates

Julkaisun otsikon käännös: Topologisten rakenteiden luonti ja dynamiikka Bosen–Einsteinin kondensaateissa

Tuomas Ollikainen

Tutkimustuotos: Doctoral Thesis › Collection of Articles

Abstrakti

Topologia tarjoaa syvällisiä käsitteellisiä yhteyksiä fysiikan eri haarojen välillä. Bosen–Einsteinin kondensaatit spin-vapausasteilla ovat yksiä monipuolisimmista systeemeistä topologisten rakenteiden tutkimukseen. Laaja kirjo kondensaatissa esiintyviä topologisia rakenteita, kuten kvanttipyörteet, monopolit, solmut ja skyrmionit, ovat analogisia sähkömagnetismissa, korkean energian fysiikassa ja kosmologiassa ennustettujen rakenteiden kanssa. Tässä väitöskirjassa tutkitaan uudenlaisia topologisten rakenteiden luomismenetelmiä sekä näiden rakenteiden dynamiikkaa laskennallisin ja kokeellisin työkaluin. Työssä näytetään kokeellisesti, kuinka eristetty monopoli kehittyy Diracin monopoliksi kvadrupolimagneettikentän läsnäollessa. Diracin monopoli ilmenee kondensaatin synteettisessä magneettikentässä ja siihen on linkittynyt spontaanisti syntyneitä nodaalilinjoja. Kvanttisolmun havaitaan hajoavan polaariytimiseksi spinpyörteeksi vakiomagneettikentässä. Lisäksi työssä havaitaan kuinka ytimettömän pyörretilan hajoaminen aiheuttaa kahden singulaarisen SO(3)-pyörteen syntymisen. Monet tutkituista topologisten rakenteiden luomismenetelmistä nojautuvat ulkoisen magneettikentän adiabaattiseen hallintaan. Vasta-adiabaattinen menetelmä tarjoaa keinon nopeuttaa tätä muutoin hidasta magneettikentän hallintaa korjaavan magneettikentän avulla. Menetelmää sovelletaan kvanttipyörteiden nopeaan pumppaukseen, johtaen korkeimman pyörimismäärän kvanttipyörteeseen, joka kondensaattiin on onnistuttu luomaan käyttämällä kokeellisesti käyttökelpoisia menetelmiä. Lisäksi näytämme kuinka kondensaattiin voidaan luoda vasta-adiabaattisella menetelmällä kvanttisolmuja. Työn eräänä päätutkimuskohteena on erilaisten skyrmionien ominaisuuksien tutkimus. Kaksiulotteisten skyrmionien simulaatiot vastaavat kvantitatiivisesti toisaalla suoritettuja kokeita ja ne selittävät kokeellisesti havaitun skyrmionin epästabiilisuuden. Eksoottisia spin-2 skyrmioneja analysoidaan laskennallisesti syklisessä ja biaksiaalisessa nemaattisessa faasissa. Erityisesti työssä esitellään Shankarin skyrmionin ensimmäinen kokeellinen havainto spin-1 kondensaateissa ja analysoidaan sen synteettisiä sähkömagneettisia ominaisuuksia. Tämän väitöskirjan tutkimus kattaa mittavan määrän topologisia rakenteita, mutta kondensaatit tarjoavat edelleen monia muita rakenteita jatkotutkimuksille. Monopoleihin, solmuihin ja skyrmioneihin liittyvien eksitaatioiden tarkka laskennallinen karakterisointi on myös kiinnostava jatkotutkimuksen kohde. Tämän väitöskirjan tulokset luovat vankan perustan topologisten rakenteiden dynamiikan kokeelliselle tutkimukselle spinorikondensaateissa.

Julkaisun otsikon käännös	Topologisten rakenteiden luonti ja dynamiikka Bosen–Einsteinin kondensaateissa
Alkuperäiskieli	Englanti
Pätevyys	Tohtorintutkinto
Myöntävä instituutio	Aalto-yliopisto
Ohjaaja	Möttönen, Mikko, Vastuuprofessori Hall, David S., Ohjaaja, Ulkoinen henkilö
Kustantaja	Aalto University
Painoksen ISBN	978-952-60-8752-8
Sähköinen ISBN	978-952-60-8753-5
Tila	Julkaistu - 2019
OKM-julkaisutyyppi	G5 Artikkeliväitöskirja

Tutkimusalat

Bosen–Einsteinin kondensaatti
topologinen rakenne

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http://urn.fi/URN:ISBN:978-952-60-8753-5

Science-IT
Hakala, M. (Manager)
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@phdthesis{af44999774d3460d974896c0d98153fb,

title = "Creation and dynamics of topological structures in Bose–Einstein condensates",

abstract = "Topology provides deep conceptual links between the various branches of physics. Bose–Einstein condensates with spin degrees of freedom are among the most accessible quantum systems available for studying topological structures. A wide range of topological defects and textures available in condensates, such as vortices, monopoles, knots, and skyrmions, are analogous to those predicted in electromagnetism, high-energy physics, and cosmology. In this dissertation, we numerically and experimentally investigate novel creation methods for topological structures and study their dynamical properties. Specifically, we experimentally observe the evolution of an isolated monopole into a Dirac monopole in the presence of a quadrupole magnetic field. The Dirac monopole appears in the synthetic magnetic field of the condensate and is accompanied by spontaneously emerging nodal lines. We observe the decay of a quantum knot into a polar-core spin vortex in the presence of a uniform magnetic field. Furthermore, we observe that a decaying coreless-vortex state gives rise to a pair of singular SO(3) vortices. Many of the studied creation methods for topological structures in the condensate rely on adiabatic control of the external magnetic field. The counterdiabatic protocol offers a way to speed up the otherwise slow magnetic field driving required for adiabatic dynamics with a correcting magnetic field. Using this method, we numerically implement a scheme for fast vortex pumping which leads to the vortex with highest angular momentum reported to date in Bose–Einstein condensates with experimentally feasible methods. We further use the counterdiabatic protocol in a novel way to create quantum knots in the condensate. Another focal point of this dissertation is the study on different types of skyrmions in spinor condensates. Our simulations of two-dimensional skyrmions are in a quantitative agreement with an experiment carried out elsewhere, explaining the experimentally observed instabilities. We numerically analyze the exotic spin-2 skyrmions available in the cyclic and biaxial nematic phases. Importantly, we present the first experimental observations of Shankar skyrmions in spin-1 condensates and analyze their synthetic electromagnetic properties. This dissertation addresses an extensive amount of topological structures available in the condensate, but many different structures await future studies. In addition, the precise computational characterization of the elementary excitations of monopoles, knots, and skyrmions is of great interest. The results of this dissertation form a sturdy basis for future experimental studies on the dynamics of topological structures in spinor condensates.",

keywords = "Bose–Einstein condensate, topological structure, Bosen–Einsteinin kondensaatti, topologinen rakenne, Bose–Einstein condensate, topological structure",

author = "Tuomas Ollikainen",

year = "2019",

language = "English",

isbn = "978-952-60-8752-8",

series = "Aalto University publication series DOCTORAL DISSERTATIONS",

publisher = "Aalto University",

number = "183",

address = "Finland",

school = "Aalto University",

}

TY - BOOK

T1 - Creation and dynamics of topological structures in Bose–Einstein condensates

AU - Ollikainen, Tuomas

PY - 2019

Y1 - 2019

N2 - Topology provides deep conceptual links between the various branches of physics. Bose–Einstein condensates with spin degrees of freedom are among the most accessible quantum systems available for studying topological structures. A wide range of topological defects and textures available in condensates, such as vortices, monopoles, knots, and skyrmions, are analogous to those predicted in electromagnetism, high-energy physics, and cosmology. In this dissertation, we numerically and experimentally investigate novel creation methods for topological structures and study their dynamical properties. Specifically, we experimentally observe the evolution of an isolated monopole into a Dirac monopole in the presence of a quadrupole magnetic field. The Dirac monopole appears in the synthetic magnetic field of the condensate and is accompanied by spontaneously emerging nodal lines. We observe the decay of a quantum knot into a polar-core spin vortex in the presence of a uniform magnetic field. Furthermore, we observe that a decaying coreless-vortex state gives rise to a pair of singular SO(3) vortices. Many of the studied creation methods for topological structures in the condensate rely on adiabatic control of the external magnetic field. The counterdiabatic protocol offers a way to speed up the otherwise slow magnetic field driving required for adiabatic dynamics with a correcting magnetic field. Using this method, we numerically implement a scheme for fast vortex pumping which leads to the vortex with highest angular momentum reported to date in Bose–Einstein condensates with experimentally feasible methods. We further use the counterdiabatic protocol in a novel way to create quantum knots in the condensate. Another focal point of this dissertation is the study on different types of skyrmions in spinor condensates. Our simulations of two-dimensional skyrmions are in a quantitative agreement with an experiment carried out elsewhere, explaining the experimentally observed instabilities. We numerically analyze the exotic spin-2 skyrmions available in the cyclic and biaxial nematic phases. Importantly, we present the first experimental observations of Shankar skyrmions in spin-1 condensates and analyze their synthetic electromagnetic properties. This dissertation addresses an extensive amount of topological structures available in the condensate, but many different structures await future studies. In addition, the precise computational characterization of the elementary excitations of monopoles, knots, and skyrmions is of great interest. The results of this dissertation form a sturdy basis for future experimental studies on the dynamics of topological structures in spinor condensates.

AB - Topology provides deep conceptual links between the various branches of physics. Bose–Einstein condensates with spin degrees of freedom are among the most accessible quantum systems available for studying topological structures. A wide range of topological defects and textures available in condensates, such as vortices, monopoles, knots, and skyrmions, are analogous to those predicted in electromagnetism, high-energy physics, and cosmology. In this dissertation, we numerically and experimentally investigate novel creation methods for topological structures and study their dynamical properties. Specifically, we experimentally observe the evolution of an isolated monopole into a Dirac monopole in the presence of a quadrupole magnetic field. The Dirac monopole appears in the synthetic magnetic field of the condensate and is accompanied by spontaneously emerging nodal lines. We observe the decay of a quantum knot into a polar-core spin vortex in the presence of a uniform magnetic field. Furthermore, we observe that a decaying coreless-vortex state gives rise to a pair of singular SO(3) vortices. Many of the studied creation methods for topological structures in the condensate rely on adiabatic control of the external magnetic field. The counterdiabatic protocol offers a way to speed up the otherwise slow magnetic field driving required for adiabatic dynamics with a correcting magnetic field. Using this method, we numerically implement a scheme for fast vortex pumping which leads to the vortex with highest angular momentum reported to date in Bose–Einstein condensates with experimentally feasible methods. We further use the counterdiabatic protocol in a novel way to create quantum knots in the condensate. Another focal point of this dissertation is the study on different types of skyrmions in spinor condensates. Our simulations of two-dimensional skyrmions are in a quantitative agreement with an experiment carried out elsewhere, explaining the experimentally observed instabilities. We numerically analyze the exotic spin-2 skyrmions available in the cyclic and biaxial nematic phases. Importantly, we present the first experimental observations of Shankar skyrmions in spin-1 condensates and analyze their synthetic electromagnetic properties. This dissertation addresses an extensive amount of topological structures available in the condensate, but many different structures await future studies. In addition, the precise computational characterization of the elementary excitations of monopoles, knots, and skyrmions is of great interest. The results of this dissertation form a sturdy basis for future experimental studies on the dynamics of topological structures in spinor condensates.

KW - Bose–Einstein condensate

KW - topological structure

KW - Bosen–Einsteinin kondensaatti

KW - topologinen rakenne

KW - Bose–Einstein condensate

KW - topological structure

M3 - Doctoral Thesis

SN - 978-952-60-8752-8

T3 - Aalto University publication series DOCTORAL DISSERTATIONS

PB - Aalto University

ER -

Creation and dynamics of topological structures in Bose–Einstein condensates

Abstrakti

Tutkimusalat

Pääsy asiakirjaan

Sormenjälki

Laitteet

Science-IT

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