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Balatsky, Alexander V.ORCID iD iconorcid.org/0000-0003-4984-889x
Alternative names
Publications (10 of 125) Show all publications
Wong, P. & Balatsky, A. V. (2023). Appearance of odd-frequency superconductivity in a relativistic scenario. Physical Review B, 108(1), Article ID 014510.
Open this publication in new window or tab >>Appearance of odd-frequency superconductivity in a relativistic scenario
2023 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 108, no 1, article id 014510Article in journal (Refereed) Published
Abstract [en]

Odd-frequency superconductivity is an exotic superconducting state in which the symmetry of the gap function is odd in frequency. Here, we show that an inherent odd-frequency mode emerges dynamically under application of a Lorentz transformation of the anomalous Green function with the general frequency-dependent gap function. To see this, we consider a Dirac model with quartic potential and perform a mean-field analysis to obtain a relativistic Bogoliubov-de Gennes system. Solving the resulting Gor'kov equations yields expressions for relativistic normal and anomalous Green functions. The form of the relativistically invariant pairing term is chosen such that it reduces to BCS form in the nonrelativistic limit. We choose an ansatz for the gap function in a particular frame which is even frequency and analyze the effects on the anomalous Green function under a boost into a relativistic frame. The odd-frequency pairing emerges dynamically as a result of the boost. In the boosted frame, the order parameter contains terms which are both even and odd in frequency. The relativistic correction to the anomalous Green function to first order in the boost parameter is completely odd in frequency. In this paper, we provide evidence that odd-frequency pairing may form intrinsically within relativistic superconductors.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:su:diva-223244 (URN)10.1103/PhysRevB.108.014510 (DOI)001060903200003 ()2-s2.0-85166956400 (Scopus ID)
Available from: 2023-11-13 Created: 2023-11-13 Last updated: 2023-11-13Bibliographically approved
Gao, J., Khaymovich, I., Iovan, A., Wang, X.-W., Krishna, G., Xu, Z.-S., . . . Elshaari, A. W. (2023). Coexistence of extended and localized states in finite-sized mosaic Wannier-Stark lattices. Physical Review B, 108(14), Article ID L140202.
Open this publication in new window or tab >>Coexistence of extended and localized states in finite-sized mosaic Wannier-Stark lattices
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2023 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 108, no 14, article id L140202Article in journal (Refereed) Published
Abstract [en]

Quantum transport and localization are fundamental concepts in condensed matter physics. It is commonly believed that in one-dimensional systems, the existence of mobility edges is highly dependent on disorder. Recently, there has been a debate over the existence of an exact mobility edge in a modulated mosaic model without quenched disorder, the so-called mosaic Wannier-Stark lattice. Here, we experimentally implement such disorder-free mosaic photonic lattices using a silicon photonics platform. By creating a synthetic electric field, we could observe energy-dependent coexistence of both extended and localized states in a finite number of waveguides. The Wannier-Stark ladder emerges when the resulting potential is strong enough, and can be directly probed by exciting different spatial modes of the lattice. Our studies provide the experimental proof of coexisting sets of strongly localized and conducting (though weakly localized) states in finite-sized mosaic Wannier-Stark lattices, which hold the potential to encode high-dimensional quantum resources with compact and robust structures.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:su:diva-224311 (URN)10.1103/PhysRevB.108.L140202 (DOI)001093993400003 ()2-s2.0-85175002919 (Scopus ID)
Available from: 2023-12-06 Created: 2023-12-06 Last updated: 2023-12-06Bibliographically approved
Bossini, D., Juraschek, D. M., Geilhufe, R. M., Nagaosa, N., Balatsky, A. V., Milanović, M., . . . Kirilyuk, A. (2023). Magnetoelectrics and multiferroics: theory, synthesis, characterisation, preliminary results and perspectives for all-optical manipulations. Journal of Physics D: Applied Physics, 56(27), Article ID 273001.
Open this publication in new window or tab >>Magnetoelectrics and multiferroics: theory, synthesis, characterisation, preliminary results and perspectives for all-optical manipulations
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2023 (English)In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 56, no 27, article id 273001Article, review/survey (Refereed) Published
Abstract [en]

Solid state compounds exhibiting multiple and coupled macroscopic orders, named multiferroics, represent a challenge for both theoretical and experimental modern condensed-matter physics. Spins and the electric polarisation in conventional magnetic and ferroelectric materials can be manipulated on their fundamental timescales, by means of femtosecond laser pulses. In view of the resounding success and popularity of the all-optical approach, it is only natural to wonder about the application of this scheme to study the intrinsic coupling between spins and charges in multiferroics. Deeply fundamental questions arise: can ultrashort laser pulses deterministically activate, enhance or suppress the magnetoelectric coupling on the femtosecond timescale? Can these processes be triggered in a fully coherent fashion, thus being unrestrained by any thermal load? Which mechanism of spin-charge coupling is most favourable to overcome these overarching and daunting challenges? This problem is interdisciplinary in nature, requiring contributions from materials science and condensed matter physics from both theoretical and experimental perspectives. High-quality materials suitable for optical investigations have to be identified, synthetized and characterised. General and valid models offer then a guide to the plethora of possible light-induced processes, resulting in the desired ultrafast multiferroic manipulations. Finally, healthy experimental schemes, able to unambiguously track the ultrafast dynamics of either the ferroelectric or the magnetic order parameter have to be developed and implemented. Our motivation to write this review is to lay a broad and multidisciplinary foundation, which may be employed as a starting point for non-equilibrium approaches to the manipulation of the multiferroicity on the femtosecond timescale. This was also one of the main goals of the COST Action MAGNETOFON, whose network constitutes the core of the authors of this review. The present work thus represents a part of the scientific legacy of MAGNETOFON itself.

Keywords
ultrafast spin dynamics, ultrafast charge dynamics, material synthesis and characterisation, multiferroics, x-ray spectroscopy, modelling and theory
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:su:diva-219583 (URN)10.1088/1361-6463/acc8e1 (DOI)000977242100001 ()2-s2.0-85154596117 (Scopus ID)
Available from: 2023-08-01 Created: 2023-08-01 Last updated: 2023-08-01Bibliographically approved
Balatsky, A. V., Fraser, B. & Røising, H. S. (2022). Dark sound: Collective modes of the axionic dark matter condensate. Physical Review D: covering particles, fields, gravitation, and cosmology, 105(2), Article ID 023504.
Open this publication in new window or tab >>Dark sound: Collective modes of the axionic dark matter condensate
2022 (English)In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 105, no 2, article id 023504Article in journal (Refereed) Published
Abstract [en]

We discuss the axion dark matter (DM) condensate and the consequences the interactions of dark matter would have on the spectrum of collective modes. We find that DM self-interactions change the spectrum of excitations from a quadratic to a linearlike dispersion with velocity vs which is set by the interactions, but dominated by gravity. For typical DM densities and interactions we find vs∼10−12c. This soundlike mode corresponds to DM density oscillations just like in any other Bose liquid, hence we call it dark sound (DS). The DS mode is well defined and describes stable density oscillations at intermediate length scales k≥kmin∼104  lyr−1. In the extreme long-wavelength limit gravity dominates and leads to Jeans instability of the sound mode at the scale of clump formation k≤kmin. We also discuss the possible observable consequences of the DS, including quantized DS modes inside clumps, their characteristic energy, and noise features that might facilitate the observation of DM.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-202022 (URN)10.1103/PhysRevD.105.023504 (DOI)000744639600008 ()
Available from: 2022-02-11 Created: 2022-02-11 Last updated: 2022-02-11Bibliographically approved
Jiang, Q.-D. & Balatsky, A. (2022). Geometric Induction in Chiral Superfluids. Physical Review Letters, 129(1), Article ID 016801.
Open this publication in new window or tab >>Geometric Induction in Chiral Superfluids
2022 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 129, no 1, article id 016801Article in journal (Refereed) Published
Abstract [en]

We explore the properties of chiral superfluid thin films coating a curved surface. Because of the vector nature of the order parameter, a geometric gauge field emerges and leads to a number of observable effects such as anomalous vortex-geometric interaction and curvature-induced mass and spin supercurrents. We apply our theory to several well-known phases of chiral superfluid 3He and derive experimentally observable signatures. We further discuss the cases of flexible geometries where a soft surface can adapt itself to compensate for the strain from the chiral superfluid. The proposed interplay between geometry and chiral superfluid order provides a fascinating avenue to control and manipulate quantum states with strain.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:su:diva-207933 (URN)10.1103/PhysRevLett.129.016801 (DOI)000828552400013 ()35841579 (PubMedID)2-s2.0-85134485947 (Scopus ID)
Available from: 2022-08-19 Created: 2022-08-19 Last updated: 2022-08-19Bibliographically approved
Olsthoorn, B., Rönnqvist, T., Lau, C., Rajasekaran, S., Persson, T., Månsson, M. & Balatsky, A. V. (2022). Indoor radon exposure and its correlation with the radiometric map of uranium in Sweden. Science of the Total Environment, 811, Article ID 151406.
Open this publication in new window or tab >>Indoor radon exposure and its correlation with the radiometric map of uranium in Sweden
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2022 (English)In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 811, article id 151406Article in journal (Refereed) Published
Abstract [en]

Indoor radon concentrations are controlled by both human factors and geological factors. It is important to separate the anthropogenic and geogenic contributions. We show that there is a positive correlation between the radiometric map of uranium in the ground and the measured radon in the household in Sweden. A map of gamma radiation is used to obtain an equivalent uranium concentration (ppm eU) for each postcode area. The aggregated uranium content is compared to the yearly average indoor radon concentration for different types of houses. Interestingly, modern households show reduced radon concentrations even in postcode areas with high average uranium concentrations. This shows that modern construction is effective at reducing the correlation with background uranium concentrations and minimizing the health risk associated with radon exposure. These correlations and predictive housing parameters could assist in monitoring higher risk areas.

Keywords
Radon risk mapping, Uranium geology, Indoor radon
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-203721 (URN)10.1016/j.scitotenv.2021.151406 (DOI)000767249400013 ()34748851 (PubMedID)2-s2.0-85119209844 (Scopus ID)
Available from: 2022-04-07 Created: 2022-04-07 Last updated: 2022-04-07Bibliographically approved
Liang, L., Sukhachov, P. O. & Balatsky, A. (2021). Axial Magnetoelectric Effect in Dirac Semimetals. Physical Review Letters, 126(24), Article ID 247202.
Open this publication in new window or tab >>Axial Magnetoelectric Effect in Dirac Semimetals
2021 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 126, no 24, article id 247202Article in journal (Refereed) Published
Abstract [en]

We propose a mechanism to generate a static magnetization via the axial magnetoelectric effect (AMEE). Magnetization M similar to E-5 (omega) x E-5* (omega) appears as a result of the transfer of the angular momentum of the axial electric field E-5(t) into the magnetic moment in Dirac and Weyl semimetals. We point out similarities and differences between the proposed AMEE and a conventional inverse Faraday effect. As an example, we estimated the AMEE generated by circularly polarized acoustic waves and find it to be on the scale of microgauss for gigahertz frequency sound. In contrast to a conventional inverse Faraday effect, magnetization rises linearly at small frequencies and fixed sound intensity as well as demonstrates a nonmonotonic peak behavior for the AMEE. The effect provides a way to investigate unusual axial electromagnetic fields via conventional magnetometry techniques.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-195828 (URN)10.1103/PhysRevLett.126.247202 (DOI)000663310900014 ()34213932 (PubMedID)
Available from: 2021-08-31 Created: 2021-08-31 Last updated: 2022-02-25Bibliographically approved
Røising, H. S., Fraser, B., Griffin, S. M., Bandyopadhyay, S., Mahabir, A., Cheong, S.-W. & Balatsky, A. (2021). Axion-matter coupling in multiferroics. Physical Review Research, 3(3), Article ID 033236.
Open this publication in new window or tab >>Axion-matter coupling in multiferroics
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2021 (English)In: Physical Review Research, E-ISSN 2643-1564, Vol. 3, no 3, article id 033236Article in journal (Refereed) Published
Abstract [en]

Multiferroics (MFs) are materials with two or more ferroic orders, like spontaneous ferroelectric and ferromagnetic polarizations. Such materials can exhibit a magnetoelectric effect whereby magnetic and ferroelectric polarizations couple linearly, reminiscent of, but not identical to the electromagnetic E . B axion coupling. Here we point out a possible mechanism in which an external dark matter axion field couples linearly to ferroic orders in these materials without external applied fields. We find the magnetic response to be linear in the axion-electron coupling. At temperatures close to the ferromagnetic transition fluctuations can lead to an enhancement of the axion-induced magnetic response. Relevant material candidates such as the Lu-Sc hexaferrite family are discussed.

Keywords
Dark matter, Ferroelectricity, Ferromagnetism
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-197892 (URN)10.1103/PhysRevResearch.3.033236 (DOI)000695729100007 ()
Available from: 2021-10-18 Created: 2021-10-18 Last updated: 2022-02-25Bibliographically approved
Sukhachov, P. O., Banerjee, S. & Balatsky, A. V. (2021). Bose-Einstein condensate of Dirac magnons: Pumping and collective modes. Physical Review Research, 3(1), Article ID 013002.
Open this publication in new window or tab >>Bose-Einstein condensate of Dirac magnons: Pumping and collective modes
2021 (English)In: Physical Review Research, E-ISSN 2643-1564, Vol. 3, no 1, article id 013002Article in journal (Refereed) Published
Abstract [en]

We explore the formation and collective modes of Bose-Einstein condensate of Dirac magnons (Dirac BEC). While we focus on two-dimensional Dirac magnons, an employed approach is general and could be used to describe Bose-Einstein condensates with linear quasiparticle spectrum in various systems. By using a phenomenological multicomponent model of pumped boson population together with bosons residing at Dirac nodes, the formation and time evolution of condensates of Dirac bosons is investigated. The condensate coherence and its multicomponent nature are manifested in the Rabi oscillations whose period is determined by the gap in the spin-wave spectrum. A Dirac nature of the condensates could be also probed by the spectrum of collective modes. It is shown that the Haldane gap provides an efficient means to tune between the gapped and gapless collective modes as well as controls their stability.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-191727 (URN)10.1103/PhysRevResearch.3.013002 (DOI)000605564000002 ()
Available from: 2021-03-31 Created: 2021-03-31 Last updated: 2022-02-25Bibliographically approved
Pertsova, A., Johnson, P., Arovas, D. P. & Balatsky, A. V. (2021). Dirac node engineering and flat bands in doped Dirac materials. Physical Review Research, 3(3), Article ID 033001.
Open this publication in new window or tab >>Dirac node engineering and flat bands in doped Dirac materials
2021 (English)In: Physical Review Research, E-ISSN 2643-1564, Vol. 3, no 3, article id 033001Article in journal (Refereed) Published
Abstract [en]

We suggest the tried approach of impurity band engineering to produce flat bands and additional nodes in Dirac materials. We show that surface impurities give rise to nearly flat impurity bands close to the Dirac point. The hybridization of the Dirac nodal state induces the splitting of the surface Dirac nodes and the appearance of new nodes at high-symmetry points of the Brillouin zone. The results are robust and not model dependent: our tight-binding calculations are supported by a low-energy effective model of a topological insulator surface state hybridized with an impurity band. Finally, we address the effects of electron-electron interactions between localized electrons on the impurity site. We confirm that the correlation effects, while producing band hybridization and the Kondo effect, keep the hybridized band flat. Our findings open up prospects for impurity band engineering of nodal structures and flat-band correlated phases in doped Dirac materials.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-196071 (URN)10.1103/PhysRevResearch.3.033001 (DOI)000669059300001 ()
Available from: 2021-09-01 Created: 2021-09-01 Last updated: 2022-02-25Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-4984-889x

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