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Spintronics and quantum transport

Spintronics investigates the ways to manipulate quantum and classical spins of a magnet with the help of electric fields and currents or with the help of optical pulses and heat flows. Spintronics effects are typically enhanced in materials with strong spin-orbit interaction.

Quantum transport is a mature field that investigates the flow of charge in small devices, typically at low temperatures, where quantum effects become more important. The field is known for such phenomena as quantum Hall effect, conductance quantization, many body and weak localization, Josephson effect, Coulomb blockade etc. In recent years the field has been influenced by the discovery of graphene and topological insulators and by the continuing search for Majorana bound states.

Recent wave of interest to a newly discovered class of two-dimensional (2D) magnets made the two fields as close as never before. In our group we develop effective models of 2D magnets and apply the ideas of quantum transport to build rather detailed microscopic theory of spintronics effects. One interesting material from our perspective is Fe3GeTe2, which can often be regarded as 2D Rashba ferromagnet. Our recent achievements include the discovery of intricate relations between Gilbert damping and spin-transfer torques [1], the importance of spin-torque anisotropy and multi-spin in-direct magnetic interactions [2-3], and strong suppression of Gilbert damping in 2D antiferromagnets due to spin-orbit interactions [4-5]. We also develop hydrodynamic approaches to non-local phenomena both in 2D magnets and in usual semimetals like graphene or Weyl materials [6] and investigate the physics of magnetic multilayers involving topological insulators [7]. We have also developed the controllable microscopic theory of anomalous Hall effect in metals [8-10], that has been missing before.

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Our methodology is based on analytical theory and modelling that is re-enforced by large-scale numerical simulations (based on kinetic equations or equations of magnetization dynamics). An essential part of the work is to construct an appropriate effective model that can capture the essence of experimentally observed phenomena. We often employ diagrammatic theory for disordered models.

[1] Anisotropy of spin-transfer torques and Gilbert damping induced by Rashba coupling, I. A. Ado, P. M. Ostrovsky, M. Titov, PRB 101, 085405 (2020)
[2] Asymmetric and symmetric exchange in a generalized 2D Rashba ferromagnet, I. A. Ado, A. Qaiumzadeh, R. A. Duine, A. Brataas, M. Titov, PRL 121, 086802 (2018)
[3] Chiral ferromagnetism beyond Lifshitz invariants, I. A. Ado, A. Qaiumzadeh, A. Brataas, M. Titov, PRB 101, 161403 (2020)
[4] Spin-orbit torques in a Rashba honeycomb antiferromagnet, R. J. Sokolewicz, S. Ghosh, D. Yudin, A. Manchon, M. Titov, PRB 100, 214403 (2019)
[5] Giant anisotropy of Gilbert damping in a Rashba honeycomb antiferromagnet, M. Baglai, R. J. Sokolewicz, A. Pervishko, M. I. Katsnelson, O. Eriksson, D. Yudin, M. Titov, PRB 101, 104403 (2020)
[6] Giant non-locality in nearly compensated 2D semimetals, S. Danz, M. Titov, B. N. Narozhny, PRB 102, 081114 (2020)
[7] Spin-torque resonance due to diffusive dynamics at a surface of topological insulator, R. J. Sokolewicz, I. A. Ado, M. I. Katsnelson, P. M. Ostrovsky, M. Titov, PRB 99, 214444 (2019)
[8] Anomalous Hall effect with massive Dirac fermions, I. A. Ado, I. A. Dmitriev, P. M. Ostrovsky, M. Titov, EPL 111, 37004 (2015)
[9] Anomalous Hall effect in 2D Rashba ferromagnet, I. A. Ado, I. A. Dmitriev, P. M. Ostrovsky, M. Titov, PRL 117, 046601 (2016)
[10] Sensitivity of anomalous Hall effect to disorder correlations, I. A. Ado, I. A. Dmitriev, P. M. Ostrovsky, M. Titov, PRB 96, 235148 (2017)