Title
Quantum kinetic theory for ultracold dipolar Fermi gases
Creator
Veljić, Vladimir, 1987-, 36826215
Copyright date
2019
Object Links
Select license
Autorstvo-Nekomercijalno-Deliti pod istim uslovima 3.0 Srbija (CC BY-NC-SA 3.0)
License description
Dozvoljavate umnožavanje, distribuciju i javno saopštavanje dela, i prerade, ako se navede ime autora na način odredjen od strane autora ili davaoca licence i ako se prerada distribuira pod istom ili sličnom licencom. Ova licenca ne dozvoljava komercijalnu upotrebu dela i prerada. Osnovni opis Licence: http://creativecommons.org/licenses/by-nc-sa/3.0/rs/deed.sr_LATN Sadržaj ugovora u celini: http://creativecommons.org/licenses/by-nc-sa/3.0/rs/legalcode.sr-Latn
Language
English
Cobiss-ID
Theses Type
Doktorska disertacija
description
Datum odbrane: 04.10.2019.
Other responsibilities
mentor
Balaž, Antun, 1973-, 13695591
član komisije
Vasić, Ivana, 1983-, 37248359
član komisije
Damnjanović, Milan, 1953-, 28714087
član komisije
Knežević, Milan O., 1952-, 22254951
Academic Expertise
Prirodno-matematičke nauke
Academic Title
-
University
Univerzitet u Beogradu
Faculty
Fizički fakultet
Alternative title
Kvantna kinetička teorija za ultrahladne dipolne Fermi gasove
Publisher
[V. Veljić ]
Format
XIV, 152 lista
description
Physics - Condensed matter physics / Fizika - Fizika kondenzovanog stanja
Abstract (en)
Interactions between particles play an important role in quantum degenerate gases.
In fact, the system’s behavior is usually largely determined by the strength, range, and
symmetry of the interactions, even if very weak. For more than two decades after the
first experimental realization of a Bose-Einstein condensate (BEC) in 1995, investigations of ultracold atomic gases have mainly considered contact-type interactions, which
model the short-range van der Waals interactions between the atoms in terms of a single
parameter, the s-wave scattering length. However, some atomic or molecules species
possess a magnetic or electric dipole moment and additionally interact among each
other via the dipole-dipole interaction (DDI), which is long-ranged and anisotropic.
Signatures of the DDI have been first observed in a BEC of chromium atoms in 2005.
In the last several years, a new class of atoms from the lanthanide series, e.g., dysprosium and erbium, with stronger dipolar properties, have come into play. This permits
a more full-fledged study of dipolar effects in BECs. Furthermore, ultracold molecules
and highly excited Rydberg atoms are other promising examples for futures studies of
systems where dipolar interaction will be even more dominant, but they still need experimental efforts to achieve the desired quantum regime. Whereas the weak DDI in a
chromium BEC is well described with the Gross-Pitaevskii equation, stronger dipolar
interactions certainly necessitate a beyond-mean-field description within a Bogoliubov
theory.
In parallel to research on bosons, cold fermions also trigger great interest because
they are actually often found in nature, e.g., within the electron gas of metals, as
neutrons of heavy stars, or as quarks in plasmas as constituent elements of composite particles. Contrary to Bose systems, quantum degeneracy in experiments is much
more difficult to achieve in Fermi systems, since s-wave scattering is absent between
identical fermions, due to the Pauli exclusion principle. It was first achieved in 1999
for alkali atoms using a technique based on the sympathetic cooling with a second spin
state, another species, or a different isotope. For highly magnetic atoms, quantum degeneracy was achieved for dysprosium in 2012 using the standard sympathetic cooling
technique, while in 2014 erbium was cooled deep into the degenerate regime using a
direct evaporative cooling mediated by dipolar collisions. This direct cooling scheme
ivallows producing very dense Fermi gas down to 10% of the Fermi temperature.
Furthermore, a novel kind of strongly dipolar quantum gases became available in
the last several years. These are weakly bound polar molecules produced from atoms
with large magnetic dipole moments, such as erbium. Only very recently a quantum
degenerate dipolar Fermi gas of potassium-rubidium molecules has been experimentally realized. Unlike previously considered magnetic systems, heteronuclear molecules
such as potassium-rubidium possess large electric dipole moments. The next natural
step is to polarize this system in a preferential direction by an external electric field,
such that the DDI dominates the behavior of the system, which would open up the
realm for experimental investigation of strong dipolar Fermi gases...
Abstract (sr)
Interakcije izmedu ˇcestica igraju vaˇznu ulogu u razumevanju ponaˇsanja degeneri- -
sanih kvantnih gasova, koje je u velikoj meri odredeno jaˇcinom, dometom i simetri- -
jama interakcija, ˇcak i ako su veoma slabe. Tokom viˇse od dve decenije nakon prve
eksperimentalne realizacije Boze-Ajnˇstajn kondenzatacije 1995. godine, istraˇzivanje
ultrahladnih atomskih gasova je uglavnom bilo fokusirano na prouˇcavanje kontaktnih interakcija izmedu atoma, ˇsto je jednoparametarski model za kratkodometne van -
der Valsove interakcije, koji kao parametar uzima u obzir samo duˇzinu rasejanja u
simetriˇcnom (s) kanalu. Medutim, neke vrste atoma ili molekula poseduju magnetni -
ili elektiˇcni dipolni moment, pa moramo da uzmemo u obzir i dipol-dipol interakcije
(DDI) izmedu ˇcestica. DDI su dugodometne i anizotropne, i njihov uticaj je prvi put -
eksperimentalno izmeren u kondenzovanom gasu atoma hroma 2005. godine. Nova
klasa atoma iz grupe lantanoida, kao ˇsto su disprozijum i erbijum, sa jaˇcim dipolnim
osobinama, postala je dostupna u poslednjih nekoliko godina. Ovo omogu´cava potpunije istraˇzivanje dipolnih efekata u Boze-Ajnˇstajn-kondenzovanim sistemima. Dalje,
ultrahladni molekuli i visoko pobudeni Ridbergovi atomi predstavljaju druge mogu´ce -
pravce za prouˇcavanje sistema u kojima ´ce dipolna interakcija biti joˇs znaˇcajnija, ali
ovo zahteva dodatne eksperimentalne napore kako bi se dostigao ˇzeljeni kvantni reˇzim.
Dok se slaba DDI izmedu atoma hroma u kondenzovanim sistemima moˇze dobro opisati -
Gros-Pitaevski jednaˇcinom, prisustvo jake DDI zahteva uraˇcunavanje efekata koji nisu
prisutni u teoriji srednjeg polja u Bogoljubovljevoj teoriji.
Paralelno sa istraˇzivanjima bozona, hladni fermioni su takode izazvali veliko in- -
teresovanje jer se ˇcesto sre´cu u prirodi, na primer u sistemima kao ˇsto je elektronski
gas u metalu, u sistemima neutrona u masivnim zvezdama, ili kao kvarkovi koji ˇcine
kvark-gluonsku plazmu u kompozitnim ˇcesticama. Za razliku od bozonskih sistema,
postizanje kvantne degeneracije u eksperimentima je mnogo teˇze za fermionske sisteme, jer zbog Paulijevog principa iskluˇcenja nema rasejanja u s-kanalu za identiˇcne
fermione. Kvantna degeneracija hladnih fermiona je ostvarena prvi put 1999. godine
za alkalne atome koriˇs´cenjem tehnike zasnovane na simpatetiˇcnom hladenju pomo´cu -
atoma u drugom spinskom stanju, druge vrste atoma, ili razliˇcitog izotopa. Kod atoma
sa jakim magnetnim momentom, kvantna degeneracija je ostvarena tek 2012. godine
viiza disprozijum, koriˇs´cenjem standardne tehnike simpatetiˇcnog hladenja, a 2014. go- -
dine za erbijum, koji je ohladen duboko u degenerisani reˇzim koriˇs´cenjem direktnog -
evaporativnog hladenja pomo´cu dipolnog rasejanja. Ova direktna tehnika hla - denja je -
omogu´cila stvaranje veoma gustog Fermi gasa na oko 10% Fermi temperature.
Pored toga, nova vrsta jako dipolnog kvantnog gasa je postala eksperimentalno
dostupna u poslednjih nekoliko godina. U pitanju su slabo vezani polarni molekuli
proizvedeni od atoma sa velikim magnetnim dipolnim momentima, kao ˇsto je erbijum.
Tek proˇsle godine je eksperimentalno realizovan i kvantno-degenerisani dipolni Fermi
gas molekula kalijum-rubidijuma. Za razliku od prethodno razmatranih magnetnih
sistema, heteronuklearni molekuli kao ˇsto je kalijum-rubidijum poseduju jak elektriˇcni
dipolni moment. Sledec´ci prirodni korak je polarizacija takvog sistema u ˇzeljenom
pravcu pomo´cu spoljaˇsnjeg elektriˇcnog polja, tako da DDI dominira u ponaˇsanju sistema. Ovo bi otvorilo novo polje za eksperimentalno istraˇzivanje Fermi gasova sa
jakom DDI...
Authors Key words
Fermi gas, dipole-dipole interaction, Fermi surface, Hartree-Fock theory
Authors Key words
Fermi gas, dipol-dipol interakcija, Fermi povrˇsina, Hartri-Fok teorija
Classification
538.9:536.933(043.3)
Type
Tekst
Abstract (en)
Interactions between particles play an important role in quantum degenerate gases.
In fact, the system’s behavior is usually largely determined by the strength, range, and
symmetry of the interactions, even if very weak. For more than two decades after the
first experimental realization of a Bose-Einstein condensate (BEC) in 1995, investigations of ultracold atomic gases have mainly considered contact-type interactions, which
model the short-range van der Waals interactions between the atoms in terms of a single
parameter, the s-wave scattering length. However, some atomic or molecules species
possess a magnetic or electric dipole moment and additionally interact among each
other via the dipole-dipole interaction (DDI), which is long-ranged and anisotropic.
Signatures of the DDI have been first observed in a BEC of chromium atoms in 2005.
In the last several years, a new class of atoms from the lanthanide series, e.g., dysprosium and erbium, with stronger dipolar properties, have come into play. This permits
a more full-fledged study of dipolar effects in BECs. Furthermore, ultracold molecules
and highly excited Rydberg atoms are other promising examples for futures studies of
systems where dipolar interaction will be even more dominant, but they still need experimental efforts to achieve the desired quantum regime. Whereas the weak DDI in a
chromium BEC is well described with the Gross-Pitaevskii equation, stronger dipolar
interactions certainly necessitate a beyond-mean-field description within a Bogoliubov
theory.
In parallel to research on bosons, cold fermions also trigger great interest because
they are actually often found in nature, e.g., within the electron gas of metals, as
neutrons of heavy stars, or as quarks in plasmas as constituent elements of composite particles. Contrary to Bose systems, quantum degeneracy in experiments is much
more difficult to achieve in Fermi systems, since s-wave scattering is absent between
identical fermions, due to the Pauli exclusion principle. It was first achieved in 1999
for alkali atoms using a technique based on the sympathetic cooling with a second spin
state, another species, or a different isotope. For highly magnetic atoms, quantum degeneracy was achieved for dysprosium in 2012 using the standard sympathetic cooling
technique, while in 2014 erbium was cooled deep into the degenerate regime using a
direct evaporative cooling mediated by dipolar collisions. This direct cooling scheme
ivallows producing very dense Fermi gas down to 10% of the Fermi temperature.
Furthermore, a novel kind of strongly dipolar quantum gases became available in
the last several years. These are weakly bound polar molecules produced from atoms
with large magnetic dipole moments, such as erbium. Only very recently a quantum
degenerate dipolar Fermi gas of potassium-rubidium molecules has been experimentally realized. Unlike previously considered magnetic systems, heteronuclear molecules
such as potassium-rubidium possess large electric dipole moments. The next natural
step is to polarize this system in a preferential direction by an external electric field,
such that the DDI dominates the behavior of the system, which would open up the
realm for experimental investigation of strong dipolar Fermi gases...
“Data exchange” service offers individual users metadata transfer in several different formats. Citation formats are offered for transfers in texts as for the transfer into internet pages. Citation formats include permanent links that guarantee access to cited sources. For use are commonly structured metadata schemes : Dublin Core xml and ETUB-MS xml, local adaptation of international ETD-MS scheme intended for use in academic documents.