Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Superfluid drag in the two-component Bose-Hubbard model
KTH, School of Engineering Sciences (SCI), Physics, Statistical Physics.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

In multicomponent superfluids and superconductors, co- and counter-flows of components have in general different properties. It was discussed in 1975 by Andreev and Bashkin, in the context of He3/He4 superfluid mixtures, that inter-particle interactions produce a dissipationless drag. The drag can be understood as a superflow of one component induced by phase gradients of the other component. Importantly the drag can be both positive (entrainment) and negative (counter-flow). The effect is known to be of crucial importance for many properties of diverse physical systems ranging from the dynamics of neutron stars, rotational responses of Bose mixtures of ultra-cold atoms to magnetic responses of multicomponent superconductors. Although there exists a substantial literature that includes the drag interaction phenomenologically, much fewer regimes are covered by quantitative studies of the microscopic origin of the drag and its dependence on microscopic parameters. Here we study the microscopic origin and strength of the drag interaction in a quantum system of two-component bosons on a lattice with short-range interaction. By performing quantum Monte-Carlo simulations of a two-component Bose-Hubbard model we obtain dependencies of the drag strength on the boson-boson interactions and properties of the optical lattice. Of particular interest are the strongly-correlated regimes where the ratio of co-flow and counter-flow superfluid stiffnesses can diverge, corresponding to the case of saturated drag.

National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
URN: urn:nbn:se:kth:diva-221080OAI: oai:DiVA.org:kth-221080DiVA, id: diva2:1173318
Note

QC 20180115

Available from: 2018-01-12 Created: 2018-01-12 Last updated: 2018-01-15Bibliographically approved
In thesis
1. Structure formation, phase transitions and drag interactions in multicomponent superconductors and superfluids
Open this publication in new window or tab >>Structure formation, phase transitions and drag interactions in multicomponent superconductors and superfluids
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Superconductivity and superfluidity are some of the most funda-mental and important phenomena of modern physics. However, muchtheoretical work for such systems so far has been restricted to the one-component case. For multicomponent systems, the spectrum of possible topological defects, their structure formation and associated phasetransitions, can all be much richer than in the one-component case, motivating theoretical studies of multicomponent systems.

In this thesis, the structure formation of vortices with complicated interactions due to multicomponent effects are considered using point-particle Monte Carlo simulations. Besides the triangular vortex latticesfound for one-component type-2 superconducting vortices, it is found that a rich plethora of structural phases is possible for vortices in mul-ticomponent systems.

Since vortices play a key role in phase transitions, the problem of phase transitions in multicomponent systems is also studied in thisthesis. It could be expected that U(1) lattice London superconductorscan only have a continuous “inverted-XY” phase transition by a Peskin-Dasgupta-Halperin duality argument for the one-component case. Itis discussed here that the non-trivial internal structure of vortices in multicomponent U(1) London superconductors can instead lead to a first-order phase transition, which is supported by large-scale parallel tempering Monte Carlo simulations. Even for such systems, wherein the ground state vortex lines are axially symmetric, thermally induced splitting of composite vortices into fractional vortices can lead to a phase separation of vortex tangles, rendering the superconducting phase transition first-order.

A similar phase separation can occur for two-component superconductors with an Andreev-Bashkin drag interaction, for which a phase separation can occur even in the ground state: the drag can cause com-posite vortices to decay into attractively interacting skyrmions. Suchdrag interactions can to a large extent influence phase transitions, rotational response and vortex structures in multicomponent systems. Thisthesis thus finishes with microscopic calculations of such an Andreev-Bashkin drag interaction in an extended Bose-Hubbard model of two-species bosons in an optical lattice, using worm quantum Monte Carlosimulations. Dependencies of the drag interaction on boson-boson in-teractions and properties of the optical lattice are characterized, andpaired phases (where only co- or counter-flow states occur) are observed.

Place, publisher, year, edition, pages
Kungliga tekniska högskolan, 2018. p. 79
Series
TRITA-FYS, ISSN 0280-316X ; 2017:78
National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-221081 (URN)978-91-7729-657-7 (ISBN)
Public defence
2018-02-09, FB42, AlbaNova, Roslagstullsbacken 21, Stockholm, 14:00 (English)
Opponent
Supervisors
Note

QC 20180115

Available from: 2018-01-15 Created: 2018-01-12 Last updated: 2018-01-15Bibliographically approved

Open Access in DiVA

No full text in DiVA

Other links

https://arxiv.org/abs/1801.03052

Authority records BETA

Sellin, KarlBabaev, Egor

Search in DiVA

By author/editor
Sellin, KarlBabaev, Egor
By organisation
Statistical Physics
Condensed Matter Physics

Search outside of DiVA

GoogleGoogle Scholar

urn-nbn

Altmetric score

urn-nbn
Total: 53 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf