Higgs bosons, half-quantum vortices, and Q-balls : an expedition in the ³He universe

Samuli Autti

Higgs bosons, half-quantum vortices, and Q-balls : an expedition in the ³He universe

Julkaisun otsikon käännös: Higgsin bosoneja, puolikvanttipyörteitä ja Q-palloja : löytöretki helium-3 -maailmankaikkeudessa

Samuli Autti

Tutkimustuotos: Doctoral Thesis › Collection of Articles

Abstrakti

Supranesteet ovat jo vuosikymmenien ajan olleet kvanttifysiikan tutkimuksen kapeassa kärjessä, erityisesti mitä tulee makroskooppisten kvantti-ilmiöiden tutkimiseen. Siinä missä tämänhetkiset suuret virtaukset fysiikan tutkimuksessa kulkevat kohti varta vasten suunniteltuja kohdesysteemejä - taustalla on kvanttitietokoneen kaltaisten kvanttilaitteiden kiihtyvä tavoittelu - supranesteytyvät heliumin isotoopit ovat perinteisesti tarjonneet luonnollisen, taipuisan ja siten likipitäen ainut-laatuisen kurkistusikkunan kvanttifysiikan monimutkaiseen maailmaan. Supraneste helium-3, johon paneudumme tässä väitöskirjassa, on täsmällisesti kuvattavissa oleva kvanttisysteemi jonka lähes loppumattomat yksityiskohdat pystytään tarkoin hallitsemaan ja ymmärtämään matemaat-tisesti. Tarkoituksenani on osoittaa, kuinka tuollaisesta monipuolisudesta nousee esiin ilmiöiden joukko, jolla on yhteyksiä kosmologian kaltaisiin kaukaisilta vaikuittaviin fysiikan aloihin. Kokeellinen Helium-3 -supranesteen käsittely edellyttää hienostuneita jäähdytys- ja mittaus-menetelmiä. Käyttämässämme pyörivässä jäähdytyslaitteessa näytteen jäähdyttäminen tapahtuu nk. ydindemagnetointiastetta käyttäen, ja mittaukset tehdään ydinmagneettista resonassia (NMR) hyödyntäen. Eräs erityisen tehokas NMR-instrumentti saadaan, kun magneettisten kvasihiuk-kasten Bosen-Einsteinin -kondensaatti vangitaan keskelle supranestenäytettä. Käytimme tätä menetelmää supranesteen magneettisten yksityiskohtien, kuten muutoin hankalasti lähestyttävien Higgsin tilojen tarkasteluun. Käytimme kondensaatteja myös itsensä liikkuessaankin koossa-pitävien, nk. Q-palloaaltojen rakentamisessa, mikä edellytti kondensaattien yksityiskohtaista ymmärtämistä ja kuvaamista sekä kokeissa, että numeerisia malleja hyödyntämällä. Magnon-kondensaatin spektri määrittyy magneettikentän profiilin ja supranesteen järjestysparametrin yhteispelin seurauksena. Kondensaatti menettää jatkuvasti energiaa pääasiassa supranesteessä muodostuvien häviöllisten spinvirtausten seurauksena. Tämä prosessi on voimakkaan lämpötilariippuva, joten sitä voidaan käyttää myös supranesteen lämpötilan mittaamisessa. Väitöskirjani huomattavin tulos on löytämämme helium-3:n puolikvanttipyörteet. Löydön tärkeyttä kuvastaa Nobelvoittaja Anthony Leggettin toteamus, että kauan etsittyjen puolikvantti-pyörteiden olemassaolo on tärkein supranestefysiikan avoin ongelma. Jo kvanttifysiikan nimi viittaa siihen, että suureet kuten energia ja liikemäärä kulloinkin tarkasteltavassa systeemissä voivat muuttua vain tietyn kokoisissa paloissa, nk. kvanteissa. Siksi ainoastaan puolikkaan nesteen kiertävän virtauksen kvantin sisältävien pyörteiden löytäminen on paitsi lähtökohtaisesti kiehtovaa, myös osoitus taustalla olevan kvanttifysiikan syvällisestä ymmärryksestä.

Julkaisun otsikon käännös	Higgsin bosoneja, puolikvanttipyörteitä ja Q-palloja : löytöretki helium-3 -maailmankaikkeudessa
Alkuperäiskieli	Englanti
Pätevyys	Tohtorintutkinto
Myöntävä instituutio	Aalto-yliopisto
Valvoja/neuvonantaja	Hakonen, Pertti, Vastuuprofessori Eltsov, Vladimir, Ohjaaja
Kustantaja	Aalto University
Painoksen ISBN	978-952-60-7394-1
Sähköinen ISBN	978-952-60-7393-4
Tila	Julkaistu - 2017
OKM-julkaisutyyppi	G5 Tohtorinväitöskirja (artikkeli)

Tutkimusalat

supraneste
puolikvanttipyörre
Q-pallo
magneettinen kvasihiukkanen
Bosen-Einsteinin -kondensaatti
Higgsin bosoni

Pääsy asiakirjaan

http://urn.fi/URN:ISBN:978-952-60-7393-4Lisenssi: Määrittelemätön

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@phdthesis{812638f6f52645c69a27e9658185820d,

title = "Higgs bosons, half-quantum vortices, and Q-balls : an expedition in the ³He universe",

abstract = "For several decades, superfluid helium has provided an almost unparalleled frontier of quantum physics research, especially in topics related to macroscopic quantum phenomena. While nowadays systems studied in quantum physics are becoming increasingly artificially engineered - the quest for quantum computers and quantum technology in general being one of the driving forces of this development - traditionally both superfluid 4He and 3He have provided a natural but versatile window to their quantum nature. Superfluid 3He, the subject of this thesis, is a quantitatively understood macroscopic quantum system of considerable yet manageable mathematical complexity. In this thesis I show how such versatility translates into a variety of emergent phenomena, touching many seemingly distant fields in physics such as cosmology. Approaching superfluid helium-3 experimentally requires sophisticated cooling and probing methodology. We have used a rotating ultra-low-temperature refrigerator, where the superfluid sample is cooled down by a nuclear demagnetisation stage and probed using nuclear magnetic resonance spectroscopy (NMR). One particularly useful NMR instrument can be constructed by trapping a Bose-Einstein condensate (BEC) of magnon quasiparticles within the superfluid. We have used such condensates in probing a variety of delicate phenomena such as other spin wave modes, including Higgs modes. We have also observed propagation of self-trapped Q-ball solitons making use of magnon BECs. These achievements required careful experimental and numerical studies of the magnon BEC. The spectrum of the magnon BEC is controlled by the profile of the external magnetic field and by the spatial variation of the superfluid order parameter. The main part of the relaxation is due to temperature dependent spin transport in the normal component of the liquid, which allows translating the magnon BEC read-out into in-situ thermometer. As perhaps the most pubilicized topic of this thesis, I explain how we discovered half-quantum vortices in superfluid helium-3, a manifestation of the topological versatility of this system. Nobel laureate Anthony Leggett recently listed finding these vortices the most important remaining open problem in the ultra-low-temperature superfluid physics. In general, the very name of quantum physics refers to the observation that fundamental concepts such as energy and momentum are quantised in the microscopic world, that is, changes in the quantities describing a physical system can only occur in finite steps, integer multiples one quantum. Therefore finding vortices carrying only half-a-quantum of circulation is not only intriguing, but manifests deep understanding of the underlying physics and quantum physics in general.",

keywords = "superfluid, helium-3, half-quantum vortex, Q-ball, magnon, Bose-Einstein condensate, self-trapping, Higgs boson, supraneste, puolikvanttipy{\"o}rre, Q-pallo, magneettinen kvasihiukkanen, Bosen-Einsteinin -kondensaatti, Higgsin bosoni, superfluid, helium-3, half-quantum vortex, Q-ball, magnon, Bose-Einstein condensate, self-trapping, Higgs boson",

author = "Samuli Autti",

year = "2017",

language = "English",

isbn = "978-952-60-7394-1",

series = "Aalto University publication series DOCTORAL DISSERTATIONS",

publisher = "Aalto University",

number = "74",

address = "Finland",

school = "Aalto University",

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TY - THES

T1 - Higgs bosons, half-quantum vortices, and Q-balls : an expedition in the ³He universe

AU - Autti, Samuli

PY - 2017

Y1 - 2017

N2 - For several decades, superfluid helium has provided an almost unparalleled frontier of quantum physics research, especially in topics related to macroscopic quantum phenomena. While nowadays systems studied in quantum physics are becoming increasingly artificially engineered - the quest for quantum computers and quantum technology in general being one of the driving forces of this development - traditionally both superfluid 4He and 3He have provided a natural but versatile window to their quantum nature. Superfluid 3He, the subject of this thesis, is a quantitatively understood macroscopic quantum system of considerable yet manageable mathematical complexity. In this thesis I show how such versatility translates into a variety of emergent phenomena, touching many seemingly distant fields in physics such as cosmology. Approaching superfluid helium-3 experimentally requires sophisticated cooling and probing methodology. We have used a rotating ultra-low-temperature refrigerator, where the superfluid sample is cooled down by a nuclear demagnetisation stage and probed using nuclear magnetic resonance spectroscopy (NMR). One particularly useful NMR instrument can be constructed by trapping a Bose-Einstein condensate (BEC) of magnon quasiparticles within the superfluid. We have used such condensates in probing a variety of delicate phenomena such as other spin wave modes, including Higgs modes. We have also observed propagation of self-trapped Q-ball solitons making use of magnon BECs. These achievements required careful experimental and numerical studies of the magnon BEC. The spectrum of the magnon BEC is controlled by the profile of the external magnetic field and by the spatial variation of the superfluid order parameter. The main part of the relaxation is due to temperature dependent spin transport in the normal component of the liquid, which allows translating the magnon BEC read-out into in-situ thermometer. As perhaps the most pubilicized topic of this thesis, I explain how we discovered half-quantum vortices in superfluid helium-3, a manifestation of the topological versatility of this system. Nobel laureate Anthony Leggett recently listed finding these vortices the most important remaining open problem in the ultra-low-temperature superfluid physics. In general, the very name of quantum physics refers to the observation that fundamental concepts such as energy and momentum are quantised in the microscopic world, that is, changes in the quantities describing a physical system can only occur in finite steps, integer multiples one quantum. Therefore finding vortices carrying only half-a-quantum of circulation is not only intriguing, but manifests deep understanding of the underlying physics and quantum physics in general.

AB - For several decades, superfluid helium has provided an almost unparalleled frontier of quantum physics research, especially in topics related to macroscopic quantum phenomena. While nowadays systems studied in quantum physics are becoming increasingly artificially engineered - the quest for quantum computers and quantum technology in general being one of the driving forces of this development - traditionally both superfluid 4He and 3He have provided a natural but versatile window to their quantum nature. Superfluid 3He, the subject of this thesis, is a quantitatively understood macroscopic quantum system of considerable yet manageable mathematical complexity. In this thesis I show how such versatility translates into a variety of emergent phenomena, touching many seemingly distant fields in physics such as cosmology. Approaching superfluid helium-3 experimentally requires sophisticated cooling and probing methodology. We have used a rotating ultra-low-temperature refrigerator, where the superfluid sample is cooled down by a nuclear demagnetisation stage and probed using nuclear magnetic resonance spectroscopy (NMR). One particularly useful NMR instrument can be constructed by trapping a Bose-Einstein condensate (BEC) of magnon quasiparticles within the superfluid. We have used such condensates in probing a variety of delicate phenomena such as other spin wave modes, including Higgs modes. We have also observed propagation of self-trapped Q-ball solitons making use of magnon BECs. These achievements required careful experimental and numerical studies of the magnon BEC. The spectrum of the magnon BEC is controlled by the profile of the external magnetic field and by the spatial variation of the superfluid order parameter. The main part of the relaxation is due to temperature dependent spin transport in the normal component of the liquid, which allows translating the magnon BEC read-out into in-situ thermometer. As perhaps the most pubilicized topic of this thesis, I explain how we discovered half-quantum vortices in superfluid helium-3, a manifestation of the topological versatility of this system. Nobel laureate Anthony Leggett recently listed finding these vortices the most important remaining open problem in the ultra-low-temperature superfluid physics. In general, the very name of quantum physics refers to the observation that fundamental concepts such as energy and momentum are quantised in the microscopic world, that is, changes in the quantities describing a physical system can only occur in finite steps, integer multiples one quantum. Therefore finding vortices carrying only half-a-quantum of circulation is not only intriguing, but manifests deep understanding of the underlying physics and quantum physics in general.

KW - superfluid

KW - helium-3

KW - half-quantum vortex

KW - Q-ball

KW - magnon

KW - Bose-Einstein condensate

KW - self-trapping

KW - Higgs boson

KW - supraneste

KW - puolikvanttipyörre

KW - Q-pallo

KW - magneettinen kvasihiukkanen

KW - Bosen-Einsteinin -kondensaatti

KW - Higgsin bosoni

KW - superfluid

KW - helium-3

KW - half-quantum vortex

KW - Q-ball

KW - magnon

KW - Bose-Einstein condensate

KW - self-trapping

KW - Higgs boson

M3 - Doctoral Thesis

SN - 978-952-60-7394-1

T3 - Aalto University publication series DOCTORAL DISSERTATIONS

PB - Aalto University

ER -

Higgs bosons, half-quantum vortices, and Q-balls : an expedition in the ³He universe

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