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Publications (10 of 14) Show all publications
Garaud, J., Corticelli, A., Silaev, M. & Babaev, E. (2018). Field-induced coexistence of s(++) and s(+/-) superconducting states in dirty multiband superconductors. Physical Review B, 97(5), Article ID 054520.
Open this publication in new window or tab >>Field-induced coexistence of s(++) and s(+/-) superconducting states in dirty multiband superconductors
2018 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 97, no 5, article id 054520Article in journal (Refereed) Published
Abstract [en]

In multiband systems, such as iron-based superconductors, the superconducting states with locking and antilocking of the interband phase differences are usually considered as mutually exclusive. For example, a dirty two-band system with interband impurity scattering undergoes a sharp crossover between the s(+/-) state (which favors phase antilocking) and the s(++) state (which favors phase locking). We discuss here that the situation can be much more complex in the presence of an external field or superconducting currents. In an external applied magnetic field, dirty two-band superconductors do not feature a sharp s(perpendicular to) -> s(++) crossover but rather awashed-out crossover to a finite region in the parameter space where both s(+/-) and s(++) states can coexist for example as a lattice or a microemulsion of inclusions of different states. The current-carrying regions such as the regions near vortex cores can exhibit an s(+/-) state while it is the s(++) state that is favored in the bulk. This coexistence of both states can even be realized in the Meissner state at the domain's boundaries featuring Meissner currents. We demonstrate that there is a magnetic-field-driven crossover between the pure s(+/-) and the s(++) states.

Place, publisher, year, edition, pages
American Physical Society, 2018
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-224695 (URN)10.1103/PhysRevB.97.054520 (DOI)000426320300004 ()2-s2.0-85043767376 (Scopus ID)
Funder
Swedish Research Council, 642-2013-7837 VR2016-06122Göran Gustafsson Foundation for Research in Natural Sciences and Medicine
Note

QC 20180326

Available from: 2018-03-26 Created: 2018-03-26 Last updated: 2018-05-15Bibliographically approved
Garaud, J., Corticelli, A., Silaev, M. & Babaev, E. (2018). Properties of dirty two-band superconductors with repulsive interband interaction: Normal modes, length scales, vortices, and magnetic response. Physical Review B, 98(1), Article ID 014520.
Open this publication in new window or tab >>Properties of dirty two-band superconductors with repulsive interband interaction: Normal modes, length scales, vortices, and magnetic response
2018 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 98, no 1, article id 014520Article in journal (Refereed) Published
Abstract [en]

Disorder in two-band superconductors with repulsive interband interaction induces a frustrated competition between the phase-locking preferences of the various potential and kinetic terms. This frustrated interaction can result in the formation of an s + is superconducting state that breaks the time-reversal symmetry. In this paper we study the normal modes and their associated coherence lengths in such materials. We especially focus on the consequences of the soft modes stemming from the frustration and time-reversal symmetry breakdown. We find that two-band superconductors with such impurity-induced frustrated interactions display a rich spectrum of physical properties that are absent in their clean counterparts. It features a mixing of Leggett's and Anderson-Higgs modes, and a soft mode with diverging coherence length at the impurity-induced second-order phase transition from s +/- / s ++ states to the s + is state. Such a soft mode generically results in long-range attractive intervortex forces that can trigger the formation of vortex clusters. We find that, if such clusters are formed, their size and internal flux density have a characteristic temperature dependence that could be probed in muon-spin-rotation experiments. We also comment on the appearance of spontaneous magnetic fields due to spatially varying impurities.

National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-232885 (URN)10.1103/PhysRevB.98.014520 (DOI)000439728000003 ()
Note

QC 20180809

Available from: 2018-08-09 Created: 2018-08-09 Last updated: 2018-11-23Bibliographically approved
Garaud, J., Silaev, M. & Babaev, E. (2017). Change of the vortex core structure in two-band superconductors at the impurity-scattering-driven s(+/-)/s(++) crossover. Physical Review B, 96(14), Article ID 140503.
Open this publication in new window or tab >>Change of the vortex core structure in two-band superconductors at the impurity-scattering-driven s(+/-)/s(++) crossover
2017 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, no 14, article id 140503Article in journal (Refereed) Published
Place, publisher, year, edition, pages
American Physical Society, 2017
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-216610 (URN)10.1103/PhysRevB.96.140503 (DOI)000412434600001 ()
Note

QC 20171110

Available from: 2017-11-10 Created: 2017-11-10 Last updated: 2017-11-29Bibliographically approved
Garaud, J., Silaev, M. & Babaev, E. (2017). Microscopically derived multi-component Ginzburg-Landau theories for s plus is superconducting state. Physica. C, Superconductivity, 533, 63-73
Open this publication in new window or tab >>Microscopically derived multi-component Ginzburg-Landau theories for s plus is superconducting state
2017 (English)In: Physica. C, Superconductivity, ISSN 0921-4534, E-ISSN 1873-2143, Vol. 533, p. 63-73Article in journal (Refereed) Published
Abstract [en]

Starting with the generic Ginzburg-Landau expansion from a microscopic N-band model, we focus on the case of a 3-band model which was suggested to be relevant to describe some iron-based superconductors. This can lead to the so-called s + is superconducting state that breaks time-reversal symmetry due to the competition between different pairing channels. Of particular interest in that context, is the case of an interband dominated pairing with repulsion between different bands. For that case we consider in detail the relevant reduced two-component Ginzburg-Landau theory. We provide detailed analysis of the ground state, length scales and topological properties of that model. Prepared for the proceedings of Vortex IX conference in Rhodes (Sept. 2015).

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2017
Keywords
Time-reversal symmetry breaking, Superconductor
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-205073 (URN)10.1016/j.physc.2016.07.010 (DOI)000395954100011 ()
Note

QC 20170626

Available from: 2017-06-26 Created: 2017-06-26 Last updated: 2017-11-07Bibliographically approved
Zyuzin, A., Garaud, J. & Babaev, E. (2017). Nematic Skyrmions in Odd-Parity Superconductors. Physical Review Letters, 119(16), Article ID 167001.
Open this publication in new window or tab >>Nematic Skyrmions in Odd-Parity Superconductors
2017 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 119, no 16, article id 167001Article in journal (Refereed) Published
Abstract [en]

We study topological excitations in two-component nematic superconductors, with a particular focus on CuxBi2Se3 as a candidate material. We find that the lowest-energy topological excitations are coreless vortices: a bound state of two spatially separated half-quantum vortices. These objects are nematic Skyrmions, since they are characterized by an additional topological charge. The inter-Skyrmion forces are dipolar in this model, i.e., attractive for certain relative orientations of the Skyrmions, hence forming multi-Skyrmion bound states.

Place, publisher, year, edition, pages
American Physical Society, 2017
Keywords
Bismuth compounds, Copper compounds, Quantum theory, Selenium compounds, Topology, Vortex flow, Bound state, Candidate materials, Odd-parity, Quantum vortex, Relative orientation, Topological charges, Topological excitations, Two-component, Superconducting materials
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-227083 (URN)10.1103/PhysRevLett.119.167001 (DOI)2-s2.0-85031929755 (Scopus ID)
Note

QC 20180517

Available from: 2018-05-17 Created: 2018-05-17 Last updated: 2019-05-10Bibliographically approved
Silaev, M., Garaud, J. & Babaev, E. (2017). Phase diagram of dirty two-band superconductors and observability of impurity-induced s plus i s state. Physical Review B, 95(2), Article ID 024517.
Open this publication in new window or tab >>Phase diagram of dirty two-band superconductors and observability of impurity-induced s plus i s state
2017 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 95, no 2, article id 024517Article in journal (Refereed) Published
Abstract [en]

We investigate the phase diagram of dirty two-band superconductors. This paper primarily focuses on the properties and observability of the time-reversal symmetry-breaking s + is superconducting states, which can be generated in two-band superconductors by interband impurity scattering. We show that such states can appear in two distinct ways. First, according to a previously discussed scenario, the s + is state can form as an intermediate phase at the impurity-driven crossover between s(+/-) and s(++) states. We show that there is a second scenario where domains of the s + is state exists in the form of an isolated dome inside the s(+/-) domain, completely detached from the transition between s(+/-) and s(++) states. We demonstrate that in both cases the s + is state generated by impurity scattering exists in an extremely small interval of impurity concentrations. Although this likely precludes direct experimental observation of the s + is state formation due to this mechanism, this physics leads to the appearance of a region inside both the s(+/-) and s(++) domains with unusual properties due to softening of normal modes.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2017
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-207914 (URN)10.1103/PhysRevB.95.024517 (DOI)000400593700009 ()2-s2.0-85012300487 (Scopus ID)
Note

QC 20170530

Available from: 2017-05-30 Created: 2017-05-30 Last updated: 2017-11-29Bibliographically approved
Garaud, J., Babaev, E., Bojesen, T. A. & Sudbo, A. (2016). Lattices of double-quanta vortices and chirality inversion in p(x) + i p(y) superconductors. Physical Review B, 94(10), Article ID 104509.
Open this publication in new window or tab >>Lattices of double-quanta vortices and chirality inversion in p(x) + i p(y) superconductors
2016 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 94, no 10, article id 104509Article in journal (Refereed) Published
Abstract [en]

We investigate the magnetization processes of a standard Ginzburg-Landau model for chiral p-wave superconducting states in an applied magnetic field. We find that the phase diagram is dominated by triangular lattices of doubly quantized vortices. Only in close vicinity to the upper critical field the lattice starts to dissociate into a structure of single-quanta vortices. The degeneracy between states with opposite chirality is broken in a nonzero field. If the magnetization starts with an energetically unfavorable chirality, the process of chirality inversion induced by the external magnetic field results in the formation of a sequence of metastable states with characteristic magnetic signatures that can be probed by standard experimental techniques.

Place, publisher, year, edition, pages
American Physical Society, 2016
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-193805 (URN)10.1103/PhysRevB.94.104509 (DOI)000383140500005 ()
Funder
Swedish Research Council, 642-2013-7837
Note

QC 20161024

Available from: 2016-10-24 Created: 2016-10-11 Last updated: 2017-11-29Bibliographically approved
Garaud, J., Silaev, M. & Babaev, E. (2016). Thermoelectric Signatures of Time-Reversal Symmetry Breaking States in Multiband Superconductors. Physical Review Letters, 116(9), Article ID 097002.
Open this publication in new window or tab >>Thermoelectric Signatures of Time-Reversal Symmetry Breaking States in Multiband Superconductors
2016 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 116, no 9, article id 097002Article in journal (Refereed) Published
Abstract [en]

We show that superconductors with broken time-reversal symmetry have very specific magnetic and electric responses to inhomogeneous heating. A local heating of such superconductors induces a magnetic field with a profile that is sensitive to the presence of domain walls and crystalline anisotropy of superconducting states. A nonstationary heating process produces an electric field and a charge imbalance in different bands. These effects can be measured and used to distinguish s + is and s + id superconducting states in the candidate materials such as Ba1-xKxFe2As2.

Place, publisher, year, edition, pages
American Physical Society, 2016
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-184957 (URN)10.1103/PhysRevLett.116.097002 (DOI)000371420600011 ()2-s2.0-84960905810 (Scopus ID)
Funder
Swedish Research Council, 642-2013-7837
Note

QC 20160407

Available from: 2016-04-07 Created: 2016-04-07 Last updated: 2017-11-30Bibliographically approved
Agterberg, D. F. & Garaud, J. (2015). Checkerboard order in vortex cores from pair-density-wave superconductivity. Physical Review B. Condensed Matter and Materials Physics, 91(10), Article ID 104512.
Open this publication in new window or tab >>Checkerboard order in vortex cores from pair-density-wave superconductivity
2015 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 91, no 10, article id 104512Article in journal (Refereed) Published
Abstract [en]

We consider competing pair-density-wave (PDW) and d-wave superconducting states in a magnetic field. We show that PDW order appears in the cores of d-wave vortices, driving checkerboard charge-density-wave (CDW) order in the vortex cores, which is consistent with experimental observations. Furthermore, we find an additional CDW order that appears on a ring outside the vortex cores. This CDW order varies with a period that is twice that of the checkerboard CDW and it only appears where both PDW and d-wave order coexist. The observation of this additional CDW order would provide strong evidence for PDW order in the pseudogap phase of the cuprates. We further argue that the CDW seen by nuclear magnetic resonance at high fields is due to a PDW state that emerges when a magnetic field is applied.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-163966 (URN)10.1103/PhysRevB.91.104512 (DOI)000351036200005 ()
Funder
Swedish Research Council, 642-2013-7837Swedish Research Council, 325-2009-7664
Note

QC 20150427

Available from: 2015-04-27 Created: 2015-04-13 Last updated: 2017-12-04Bibliographically approved
Garaud, J. & Babaev, E. (2015). Properties of skyrmions and multi-quanta vortices in chiral p-wave superconductors. Scientific Reports, 5, Article ID 17540.
Open this publication in new window or tab >>Properties of skyrmions and multi-quanta vortices in chiral p-wave superconductors
2015 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 5, article id 17540Article in journal (Refereed) Published
Abstract [en]

Chiral p-wave superconducting state supports a rich spectrum of topological excitations different from those in conventional superconducting states. Besides domain walls separating different chiral states, chiral p-wave state supports both singular and coreless vortices also interpreted as skyrmions. Here, we present a numerical study of the energetic properties of isolated singular and coreless vortex states as functions of anisotropy and magnetic field penetration length. In a given chiral state, single quantum vortices with opposite winding have different energies and thus only one kind is energetically favoured. We find that with the appropriate sign of the phase winding, two-quanta (coreless) vortices are always energetically preferred over two isolated single quanta (singular) vortices. We also report solutions carrying more flux quanta. However those are typically more energetically expensive/metastable as compared to those carrying two flux quanta.

Place, publisher, year, edition, pages
Nature Publishing Group, 2015
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-180222 (URN)10.1038/srep17540 (DOI)000365689800002 ()26631985 (PubMedID)2-s2.0-84949033755 (Scopus ID)
Note

QC 20160119

Available from: 2016-01-19 Created: 2016-01-08 Last updated: 2017-11-30Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-5087-3115

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