Vendredi 28 février 2020 à 14h00, Annika Johansson (Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, Germany) donnera un séminaire sur "Spin-orbit driven transport : Edelstein effect and chiral anomaly"
Abstract :
Whereas conventional semiconductor technology is based on transport of electric charge, the main concept of the field of spintronics is to additionally utilize the spin degree of freedom for storage, processing and transfer of data. Therefore, one aim of research is to identify mechanisms and methods of efficiently generating and controlling spin(-polarized) currents as well as spin polarization. In the field of spin-orbitronics phenomena whose crucial underlying interaction is spin-orbit coupling are considered.
One spin-orbitronic phenomenon realizing charge-to-spin conversion is the Edelstein effect [1,2]. In nonmagnetic systems with broken inversion symmetry, an external electric field can induce a homogeneous spin density. Using semiclassical Boltzmann transport theory, we discuss the Edelstein effect in Rashba systems as well as topological insulators [3] and identify Weyl semimetals as candidates for providing an enormous Edelstein efficiency [4]. Further, the unconventional spin-to-charge conversion in the two-dimensional electron gas at an AlO/SrTiO3 interface is analyzed [5].
Another effect providing the interconversion of magnetic and electric properties is the chiral anomaly. It describes the nonconservation of chiral charge due to external nonorthogonal magnetic and electric fields. The chiral anomaly can be realized in Weyl semimetals and usually leads to a negative longitudinal magnetoresistance [6,7]. We discuss the transport properties of anisotropic Weyl systems and identify mechanisms leading to a sign change of the longitudinal magnetoresistance [8].
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[3] A. Johansson et al., Phys. Rev.B 93, 195440 (2016)
[4] A. Johansson et al., Phys. Rev.B 97, 085417 (2018)
[5] D. Vaz et al., Nat. Mater. 18, 1187 (2019)
[5] H. Nielsen and M. Ninomiya, Phys. Lett. B 130, 389 (1983)
[6] D. T. Son and B. Z. Spivak, Phys. Rev. B 88, 104412 (2013)
[7] A. Johansson et al., Phys. Rev. B 99, 075114 (2019)
