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Publications (10 of 21) Show all publications
Barkman, M., Zyuzin, A. A. & Babaev, E. (2019). Antichiral and nematicity-wave superconductivity. Physical Review B, 99(22), Article ID 220508.
Open this publication in new window or tab >>Antichiral and nematicity-wave superconductivity
2019 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 99, no 22, article id 220508Article in journal (Refereed) Published
Abstract [en]

Larkin-Ovchinnikov superconducting state has spontaneous modulation of Cooper pair density, while Fulde-Ferrell state has a spontaneous modulation in the phase of the order parameter. We report that a quasi-two-dimensional Dirac metal, under certain conditions has principally different inhomogeneous superconducting states that by contrast have spontaneous modulation in a submanifold of a multiple-symmetries-breaking order parameter. The first state we find can be viewed as a nematic superconductor where the nematicity vector spontaneously breaks rotational and translational symmetries due to spatial modulation. The other demonstrated state is a chiral superconductor with spontaneously broken time-reversal and translational symmetries. It is characterized by an order parameter, which forms a lattice pattern of alternating chiralities.

Place, publisher, year, edition, pages
American Physical Society, 2019
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-255306 (URN)10.1103/PhysRevB.99.220508 (DOI)000473014100002 ()2-s2.0-85068623245 (Scopus ID)
Note

QC 20190729

Available from: 2019-07-29 Created: 2019-07-29 Last updated: 2019-07-29Bibliographically approved
Winyard, T., Silaev, M. & Babaev, E. (2019). Hierarchies of length-scale based typology in anisotropic U(1) s-wave multiband superconductors. Physical Review B, 99(6), Article ID 064509.
Open this publication in new window or tab >>Hierarchies of length-scale based typology in anisotropic U(1) s-wave multiband superconductors
2019 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 99, no 6, article id 064509Article in journal (Refereed) Published
Abstract [en]

Since Ginzburg and Landau's seminal work in 1950, superconducting states have been classified by the hierarchy of the fundamental length scales of the theory, the magnetic-field penetration lengths and coherence lengths. In the simplest single-component case they form a dimensionless ratio kappa. The model was generalized by Ginzburg for anisotropic materials in 1952. In this paper we expand the above length-scale analysis to anisotropic multicomponent superconductors that can have multiple coherence lengths as well as multiple magnetic-field penetration lengths, leading to unconventional length-scale hierarchies. We demonstrate that the anisotropies in multiband superconductors lead to new regimes with various mixed hierarchies in different directions. For example, a regime is possible, where for a field applied in a certain direction coherence lengths are smaller than the magnetic-field penetration lengths in one of the perpendicular directions, whereas the penetration lengths are larger in the other direction. Focusing on a model of a clean anisotropic multiband s-wave supercocoductors we show exampes of a new regime where vortex cores overlap in one direction, resulting in attractive core-core interaction, while in the orthogonal direction the magnetic-field penetration length exceeds the coherence lengths, leading to dominance of repulsive current-current interaction, resulting in an unconventional magnetic response.

Place, publisher, year, edition, pages
American Physical Society, 2019
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-245914 (URN)10.1103/PhysRevB.99.064509 (DOI)000459222700014 ()2-s2.0-85061987792 (Scopus ID)
Note

QC 20190318

Available from: 2019-03-18 Created: 2019-03-18 Last updated: 2019-08-27Bibliographically approved
Wang, W., Díaz-Méndez, R., Wallin, M., Lidmar, J. & Babaev, E. (2019). Melting of a two-dimensional monodisperse cluster crystal to a cluster liquid. Physical review. E, 99(4), Article ID 042140.
Open this publication in new window or tab >>Melting of a two-dimensional monodisperse cluster crystal to a cluster liquid
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2019 (English)In: Physical review. E, ISSN 2470-0045, E-ISSN 2470-0053, Vol. 99, no 4, article id 042140Article in journal (Refereed) Published
Abstract [en]

Monodisperse ensembles of particles that have cluster crystalline phases at low temperatures can model a number of physical systems, such as vortices in type-1.5 superconductors, colloidal suspensions, and cold atoms. In this work, we study a two-dimensional cluster-forming particle system interacting via an ultrasoft potential. We present a simple mean-field characterization of the cluster-crystal ground state, corroborating with Monte Carlo simulations for a wide range of densities. The efficiency of several Monte Carlo algorithms is compared, and the challenges of thermal equilibrium sampling are identified. We demonstrate that the liquid to cluster-crystal phase transition is of first order and occurs in a single step, and the liquid phase is a cluster liquid. © 2019 American Physical Society.

Place, publisher, year, edition, pages
American Physical Society, 2019
Keywords
Ground state, Intelligent systems, Liquids, Suspensions (fluids), Colloidal suspensions, Crystal phase transition, Crystalline phasis, Monodisperse clusters, Monte carlo algorithms, Particle systems, Thermal equilibriums, Two-dimensional clusters, Monte Carlo methods
National Category
Materials Chemistry
Identifiers
urn:nbn:se:kth:diva-255902 (URN)10.1103/PhysRevE.99.042140 (DOI)2-s2.0-85064828694 (Scopus ID)
Note

Export Date: 24 May 2019; Article; Funding details: 621-2012-3984; Funding details: Vetenskapsrådet, 642-2013-7837; Funding text 1: W.W. and E.B. acknowledge support from the Swedish Research Council Grant No. 642-2013-7837 and the Goran Gustafsson Foundation for Research in Natural Sciences and Medicine. M.W. and R.D.M. acknowledge support from the Swedish Research Council Grant No. 621-2012-3984. The computations were performed on resources provided by the Swedish National Infrastructure for Computing (SNIC) at the National Supercomputer Centre (NSC) and the High Performance Computing Center North (HPC2N).

Available from: 2019-08-22 Created: 2019-08-22 Last updated: 2019-08-22Bibliographically approved
Diaz-Mendez, R., Pupillo, G., Mezzacapo, F., Wallin, M., Lidmar, J. & Babaev, E. (2019). Phase-change switching in 2D via soft interactions. Soft Matter, 15(3), 355-358
Open this publication in new window or tab >>Phase-change switching in 2D via soft interactions
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2019 (English)In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 15, no 3, p. 355-358Article in journal (Refereed) Published
Abstract [en]

We present a new type of phase-change behavior relevant for information storage applications, that can be observed in 2D systems with cluster-forming ability. The temperature-based control of the ordering in 2D particle systems depends on the existence of a crystal-to-glass transition. We perform molecular dynamics simulations of models with soft interactions, demonstrating that the crystalline and amorphous structures can be easily tuned by heat pulses. The physical mechanism responsible for this behavior is a self-assembled polydispersity, that depends on the cluster-forming ability of the interactions. Therefore, the range of real materials that can perform such a transition is very wide in nature, ranging from colloidal suspensions to vortex matter. The state of the art in soft matter experimental setups, controlling interactions, polydispersity and dimensionality, makes it a very fertile ground for practical applications.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2019
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-244117 (URN)10.1039/c8sm01738g (DOI)000457278300001 ()30556570 (PubMedID)2-s2.0-85060062234 (Scopus ID)
Note

QC 20190219

Available from: 2019-02-19 Created: 2019-02-19 Last updated: 2019-05-10Bibliographically approved
Winyard, T., Silaev, M. & Babaev, E. (2019). Skyrmion formation due to unconventional magnetic modes in anisotropic multiband superconductors. Physical Review B, 99(2), Article ID 024501.
Open this publication in new window or tab >>Skyrmion formation due to unconventional magnetic modes in anisotropic multiband superconductors
2019 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 99, no 2, article id 024501Article in journal (Refereed) Published
Abstract [en]

Multiband superconductors have a sufficient number of degrees of freedom to allow topological excitations characterized by skyrmionic topological invariants. In the most common, clean s-wave multiband systems, the interband Josephson and magnetic couplings favor composite vortex solutions, without a skyrmionic topological charge. It was discussed recently that certain kinds of anisotropies lead to hybridization of the interband phase difference (Leggett) mode with magnetic modes, dramatically changing the hydromagnetostatics of the system. Here we report this effect for a range of parameters that substantially alter the nature of the topological excitations, leading to solutions characterized by a nontrivial skyrmionic topological charge. The solutions have a form of a coreless texture formed of spatially separated but bound excitations in each band, namely fractional vortices, each carrying a fraction of the flux quantum. We demonstrate that in this regime there is a rich spectrum of skyrmion solutions, with various topological charges, that are robust with respect to changes of parameters of the system and present for a wide range of anisotropies.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2019
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-241318 (URN)10.1103/PhysRevB.99.024501 (DOI)000454765400006 ()2-s2.0-85059907714 (Scopus ID)
Note

QC 20190125

Available from: 2019-01-25 Created: 2019-01-25 Last updated: 2019-05-10Bibliographically approved
Bommer, J. D. S., Zhang, H., Gul, O., Nijholt, B., Wimmer, M., Rybakov, F. N., . . . Kouwenhoven, L. P. (2019). Spin-Orbit Protection of Induced Superconductivity in Majorana Nanowires. Physical Review Letters, 122(18), Article ID 187702.
Open this publication in new window or tab >>Spin-Orbit Protection of Induced Superconductivity in Majorana Nanowires
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2019 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 122, no 18, article id 187702Article in journal (Refereed) Published
Abstract [en]

Spin-orbit interaction (SOI) plays a key role in creating Majorana zero modes in semiconductor nanowires proximity coupled to a superconductor. We track the evolution of the induced superconducting gap in InSb nanowires coupled to a NbTiN superconductor in a large range of magnetic field strengths and orientations. Based on realistic simulations of our devices, we reveal SOI with a strength of 0.15-0.35 eV angstrom. Our approach identifies the direction of the spin-orbit field, which is strongly affected by the superconductor geometry and electrostatic gates.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2019
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-252376 (URN)10.1103/PhysRevLett.122.187702 (DOI)000467404500003 ()2-s2.0-85065836132 (Scopus ID)
Note

QC 20190718

Available from: 2019-07-18 Created: 2019-07-18 Last updated: 2019-10-21Bibliographically approved
Rybakov, F. N., Garaud, J. & Babaev, E. (2019). Stable Hopf-Skyrme topological excitations in the superconducting state. Physical Review B, 100(9), Article ID 094515.
Open this publication in new window or tab >>Stable Hopf-Skyrme topological excitations in the superconducting state
2019 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 100, no 9, article id 094515Article in journal (Refereed) Published
Abstract [en]

At large scales, magnetostatics of superconductors is described by a massive vector field theory: the London model. The magnetic field cannot penetrate into the bulk unless quantum vortices are formed. These are topological excitations characterized by an invariant: the phase winding. The London model dictates that loops of such vortices are not stable because the kinetic energy of superflow and the magnetic energy are smaller, the smaller vortex loops are. We demonstrate that in two-component superconductors, under certain conditions, such as the proximity to pair-density-wave instabilities, the hydromagnetostatics of the superconducting state and topological excitation changes dramatically: the excitations acquire the form of stable vortex loops and knots characterized by the different topological invariant: the Hopf index and hence termed hopfions. This demonstrates that magnetic properties in a superconducting state can be dramatically different from those of a London's massive vector field theory.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2019
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-261010 (URN)10.1103/PhysRevB.100.094515 (DOI)000485189900003 ()
Note

QC 20191003

Available from: 2019-10-03 Created: 2019-10-03 Last updated: 2019-10-03Bibliographically approved
Barkman, M., Samoilenka, A. & Babaev, E. (2019). Surface Pair-Density-Wave Superconducting and Superfluid States. Physical Review Letters, 122(16), Article ID 165302.
Open this publication in new window or tab >>Surface Pair-Density-Wave Superconducting and Superfluid States
2019 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 122, no 16, article id 165302Article in journal (Refereed) Published
Abstract [en]

Fulde, Ferrell, Larkin, and Ovchinnikov (FFLO) predicted inhomogeneous superconducting and superfluid ground states, spontaneously breaking translation symmetries. In this Letter, we demonstrate that the transition from the FFLO to the normal state as a function of temperature or increased Fermi surface splitting is not a direct one. Instead, the system has an additional phase transition to a different state where pair-density-wave superconductivity (or superfluidity) exists only on the boundaries of the system, while the bulk of the system is normal. The surface pair-density-wave state is very robust and exists for much larger fields and temperatures than the FFLO state.

Place, publisher, year, edition, pages
American Physical Society, 2019
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-251711 (URN)10.1103/PhysRevLett.122.165302 (DOI)000466440800002 ()31075028 (PubMedID)2-s2.0-85065146221 (Scopus ID)
Note

QC 20190521

Available from: 2019-05-21 Created: 2019-05-21 Last updated: 2019-05-21Bibliographically approved
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
Silaev, M., Winyard, T. & Babaev, E. (2018). Non-London electrodynamics in a multiband London model: Anisotropy-induced nonlocalities and multiple magnetic field penetration lengths. Physical Review B, 97(17), Article ID 174504.
Open this publication in new window or tab >>Non-London electrodynamics in a multiband London model: Anisotropy-induced nonlocalities and multiple magnetic field penetration lengths
2018 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 97, no 17, article id 174504Article in journal (Refereed) Published
Abstract [en]

The London model describes strongly type-2 superconductors as massive vector field theories, where the magnetic field decays exponentially at the length scale of the London penetration length. This also holds for isotropic multiband extensions, where the presence of multiple bands merely renormalizes the London penetration length. We show that, by contrast, the magnetic properties of anisotropic multiband London models are not this simple, and the anisotropy leads to the interband phase differences becoming coupled to the magnetic field. This results in the magnetic field in such systems having N + 1 penetration lengths, where N is the number of field components or bands. That is, in a given direction, the magnetic field decay is described by N + 1 modes with different amplitudes and different decay length scales. For certain anisotropies we obtain magnetic modes with complex masses. That means that magnetic field decay is not described by a monotonic exponential increment set by a real penetration length but instead is oscillating. Some of the penetration lengths are shown to diverge away from the superconducting phase transition when the mass of the phase-difference mode vanishes. Finally the anisotropy-driven hybridization of the London mode with the Leggett modes can provide an effectively nonlocal magnetic response in the nominally local London model. Focusing on the two-component model, we discuss the magnetic field inversion that results from the effective nonlocality, both near the surface of the superconductor and around vortices. In the regime where the magnetic field decay becomes nonmonotonic, the multiband London superconductor is shown to form weakly-bound states of vortices.

Place, publisher, year, edition, pages
American Physical Society, 2018
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-228434 (URN)10.1103/PhysRevB.97.174504 (DOI)000431986100003 ()2-s2.0-85047258709 (Scopus ID)
Note

QC 20180529

Available from: 2018-05-29 Created: 2018-05-29 Last updated: 2018-11-23Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-7593-4543

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