Seminar experimentelle Physik der kondensierten Materie

Programm für das Wintersemester 2023/2024

Thursdays, 14:00 Uhr s.t.

01 122 Newton-Raum

04.10.23Paul J. Kelly, University of Twente
Phenomenological theories in spintronics are usually based upon semiclassical formulations of transport like the Boltzmann or diffusion equations that cannot easily accommodate the fundamentally quantum character of energy bands and Fermi surfaces; this is more readily done using scattering theory. The challenge for first-principles scattering theory is to describe the diffusive regime in which most experiments are performed. I sketch the developments that have allowed us to realize this goal culminating in the extraction of charge and spin currents [1] from large scale relativistic scattering calculations [2] that include temperature-induced lattice and spin disorder [3]. I illustrate our approach with a study of the temperature dependence of the spin-flip diffusion length and spin Hall angle for the bulk 5d transition metals [4]. It allowed us to evaluate the transport parameters required to describe a spin current through interfaces between two non-magnetic metals or between a non-magnetic and a ferromagnetic metal and focus on the temperature dependence of the spin memory loss that describes interface spin flipping [5]. When we use it to study the spin Hall effect in a thin Pt film, we find that we cannot recover the bulk spin-flip diffusion length without taking surface effects into account. The same approach allows us to examine the shunting of a charge current passed through a bilayer parallel to the interface [1], the Fuchs-Sondheimer suppression of charge currents by surfaces and interfaces [1] or the efficiency with which a spin or orbital Hall current is injected laterally from e.g Pt into Au or from Co or Py into Cu. Work carried out in collaboration with Rohit Nair, Max Rang, K. Gupta, R.J.H. Wesselink, R.X. Liu, Z. Yuan and E. Barati [1] R.J.H. Wesselink et al., PRB 99, 144409 (2019); R.S. Nair and P.J. Kelly, PRB 103, 195406 (2021). [2] A. A. Starikov et al., PRB 97, 214415 (2018). [3] Y. Liu et al., PRB 91, 220405 (2015). [4] R.S. Nair et al. PRL 126, 196601 (2021). [5] K. Gupta et al., PRL 124, 087702 (2020); PRB 104, 205426 (2021); PRB 106, 104401 (2022); PRB 106, 115425 (2022).
13:00 Uhr s.t., tba.

13.12.23Dr. Jun'ichi Ieda, Japan Atomic Energy Agency (JAEA)
Emergent inductance appears universally when magnetization dynamics is coupled with conduction electrons based on a sequential action of spin torque and spinmotive force effects under ac currents. An original version of the emergent inductor using > a spiral magnet[1-4] can be extended to include the spin-orbit coupling effects[5,6]. A striking common feature among emergent inductors is their size dependence of the effect; the inductance is inversely proportional to the sample cross-sectional area, opening > a way for integrating an inductor element into nanocircuits. > > 1. Nagaosa, N. “Emergent inductor by spiral magnets,” Jpn. J. Appl. Phys., Vol. 58, 120909, 2019. > 2. Yokouchi, T. et al., “Emergent electromagnetic induction in a helical-spin magnet,” Nature, Vol. 586, 232-236, 2020. > 3. Ieda, J. and Y. Yamane, “Intrinsic and extrinsic tunability of Rashba spin-orbit coupled emergent inductors,” Phys. Rev. B, Vol. 103,. L100402, 2021. > 4. Kitaori, A. et al., “Emergent electromagnetic induction beyond room temperature,” Proc. Natl. Acad. Sci. U.S.A., Vol. 118, e2105422118, 2021. > 5. Yamane, Y., S. Fukami, and J. Ieda, “Theory of emergent inductance with spin-orbit coupling effects,” Phys. Rev. Lett., Vol. 128, 147201, 2022. > 6. Araki, Y. and J. Ieda, “Emergence of inductance and capacitance from topological electromagnetism,” J. Phys. Soc. Jpn., Vol. 92, 074705, 2023.
13:00 Uhr s.t., 01-122 Newton Raum

SFB Sonderseminar

01.02.24Huaiyang YUAN, TU Delft and Zhejiang University
There is a rising interest in integrating magnetic systems with known quantum platforms for multi-functional quantum information processing. The coupling among magnons, photons, phonons, and qubits has already been proposed and demonstrated in the experiments. In this talk, I will introduce our recent results on the interplay of magnons and surface plasmons in two-dimensional systems. Our findings may open a novel route to integrate plasmonic and spintronic devices and bridge the fields of low-dimensional physics, plasmonics, and spintronics.
14:00 Uhr s.t., 01 122 Newton-Raum


Univ-Prof. Dr. Jure Demsar
Univ.-Prof. Dr. Hans-Joachim Elmers
Univ.-Prof. Dr. Mathias Kläui
Univ.-Prof. Dr. Thomas Palberg