In this project, we investigate the coupling of the spin degree of freedom with electronic degrees of freedom across interfaces in ferromagnetic multilayers on the ultrafast time scale. For this purpose, we consider the excitation of the ferromagnetic material by a femtosecond laser pulse. The so created spin-polarized electrons with large energies respond to the applied field which is reflected in the longitudinal and transverse transport coefficients. We consider mainly the energy-dependent transversal transport properties, that are related to the anomalous and the spin Hall effect. In particular, we are interested in the time and spatial dependence of the charge- and spin-current distribution with respect to the interface. On the other hand, we investigate timedependent spin currents that are produced by the spin Hall effect if a THz electric field is applied to the nonmagnetic metal layer. Propagation of this spin current into the ferromagnetic layer causes a spin-transfer torque on the magnetization. Based on an ab initio description in combination with a semi-classical Boltzmann theory we aim at understanding the charge and spin current distributions on nanometer length scales and ultrafast time scales.

Publications (1^st Funding Period 2018 - 2021)

• Colossal topological Hall effect at the transition between isolated and lattice-phase interfacial skyrmions 
  M. Raju, A. P. Petrović, A. Yagil, K. S. Denisov, N. K. Duong, B. Göbel, E.Şaşıoğlu, O. M. Auslaender, I. Mertig, I. V. Rozhansky, and C. Panagopoulos  
  Nat. Commun. 12: 2758 (2021)  - DOI: 10.1038/s41467-021-22976-6

• Broadband terahertz probes of anisotropic magnetoresistance disentangle extrinsic and intrinsic contributions 
  L. Nadvorník, M. Borchert, L. Brandt, R. Schlitz, K. A. de Mare, K. Výborný, I. Mertig, G. Jakob, M. Kläui, S. T. B. Goennenwein, M. Wolf, G. Woltersdorf, and T. Kampfrath
  Phys. Rev. X 11, 021030 (2021)  - DOI: 10.1103/PhysRevX.11.021030

• Ultrafast spin dynamics in inhomogeneous systems: a density-matrix approach applied to Co/Cu interfaces 
  F. Töpler, J. Henk, and I. Mertig
  New J. Phys. 23, 033042 (2021)  - DOI: 10.1088/1367-2630/abe72b

• Spin and orbital Edelstein effects in a two-dimensional electron gas: Theory and application to SrTiO₃ interfaces 
  A. Johansson, B. Göbel, J. Henk, M. Bibes, and I. Mertig 
  Phys. Rev. Res. 3, 0132275 (2021)  - DOI: 10.1103/PhysRevResearch.3.013275

• Beyond skyrmions: Review and perspectives of alternative magnetic quasiparticles 
  B. Göbel, I. Mertig, and O. A.Tretiakov 
  Phys. Rep. 895, 1 (2021)  - DOI: 10.1016/j.physrep.2020.10.001

• Skyrmion ratchet propagation: utilizing the skyrmion Hall effect in AC racetrack storage devices 
  B. Göbel and I. Mertig 
  Sci. Rep. 11 : 3020 (2021)  - DOI: 10.1038/s41598-021-81992-0

• First principles design of Ohmic spin diodes based on quaternary Heusler compounds 
  T. Aull, E. Şaşıoğlu, and I. Mertig 
  Appl. Phys. Lett. 118, 052405 (2021)  - DOI: 10.1063/5.0037085

• Terahertz spin-to-charge conversion by interfacial skew scattering in metallic bilayers
  O. Gueckstock, L. Nádvorník, M. Gradhand, T. S. Seifert, G. Bierhance, R. Rouzegar, M. Wolf, M. Vafaee, J. Cramer, M. A. Syskaki, G. Woltersdorf, I. Mertig, G. Jakob, M. Kläui, and T. Kampfrath
  Adv. Mater. 33, 2006281 (2021) - DOI: 10.1002/adma.202006281

• Evolution and competition between chiral spin textures in nanostripes with D-2d symmetry 
  J. Jena, B. Göbel, V. Kumar, I. Mertig, C. Felser, and S. S. P. Parkin
  Sci Adv. 6 : eabc0723 (2020)  - DOI: 10.1126/sciadv.abc0723

• Topological Hall signatures of two chiral spin textures hosted in a single tetragonal inverse Heusler thin film 
  P. K. Sivakumar, B. Göbel, E. Lesne, A. Markou, J. Gidugu, J. M. Taylor, H. Deniz, J. Jena, C. Felser, I. Mertig, and S. S. P. Parkin 
  ACS Nano 14, 13463 (2020) - DOI: 10.1021/acsnano.0c05413

• Impact of crystalline anisotropy on the extrinsic spin Hall effect in ultrathin films 
  C. Herschbach, D. V. Fedorov, M. Gradhand, and I. Mertig 
  Phys. Rev. B 102, 104421 (2020)  - DOI: 10.1103/PhysRevB.102.104421

• Orbital magnetic moment of magnons 
  R. R. Neumann, A. Mook, J. Henk, and I. Mertig 
  Phys. Rev. Lett. 125, 117209 (2020)  - DOI: 10.1103/PhysRevLett.125.117209

• Unconventional charge–spin conversion in Weyl-semimetal WTe₂
  B. Zhao, B. Karpiak, D. Khokhriakov, A. Johansson, A. Md. Hoque, X. Xu, Y. Jiang, I. Mertig, and S. P. Dash 
  Adv. Mater. 32, 2000818 (2020)  - DOI: 10.1002/adma.202000818

• Half-metal–spin-gapless-semiconductor junctions as a route to the ideal diode 
  E. Şaşıoğlu, T. Aull, D. Kutschabsky, S. Blügel, and I. Mertig 
  Phys. Rev. Appl. 14, 014082 (2020) - DOI: 10.1103/PhysRevApplied.14.014082

• Microscopic origin of the anomalous Hall effect in noncollinear kagome magnets 
  O. Busch, B. Göbel, and I. Mertig
  Phys. Rev. Res. 2, 033112 (2020)  - DOI: 10.1103/PhysRevResearch.2.033112

• Topological Hall signatures of magnetic hopfions
  B. Göbel, C. A. Akosa, G. Tatara, and I. Mertig 
  Phys. Rev. Res. 2, 013315 (2020)  - DOI: 10.1103/PhysRevResearch.2.013315

• Determining the Rashba parameter from the bilinear magnetoresistance response in a two-dimensional electron gas 
  D. C. Vaz, F. Trier, A. Dyrdał, A. Johansson, K. Garcia, A. Barthélémy, I. Mertig, J. Barnaś, A. Fert, and M. Bibes 
  Phys. Rev. Mater. 4, 071001(R) (2020)  - DOI: 10.1103/PhysRevMaterials.4.071001

• Origin of the magnetic spin Hall effect: Spin current vorticity in the Fermi sea 
  A. Mook, R. R. Neumann, A. Johansson, J. Henk, and I. Mertig  
  Phys. Rev. Res. 2, 023065 (2020)  - DOI: 10.1103/PhysRevResearch.2.023065

• Local spin Hall conductivity 
  T. Rauch, F. Töpler, and I. Mertig 
  Phys. Rev. B 101, 264206 (2020)  - DOI: 10.1103/PhysRevB.101.064206

• Elliptical Bloch skyrmion chiral twins in an antiskyrmion system 
  J. Jena, B. Göbel, T. Ma, V. Kumar, R. Saha, I. Mertig, C. Felser, and S. S. P. Parkin
  Nat. Commun. 11: 1115 (2020)  - DOI: 10.1038/s41467-020-14925-6

• Ab initio design of quaternary Heusler compounds for reconfigurable magnetic tunnel diodes and transistors
  T. Aull, E. Şaşıoğlu, I. V. Maznichenko, S. Ostanin, A. Ernst, I. Mertig, and I. Galanakis 
  Phys. Rev. Mater. 3, 124415 (2019)  - DOI: 10.1103/PhysRevMaterials.3.124415

• Spin Seebeck and spin Nernst effects of magnons in noncollinear antiferromagnetic insulators 
  A. Mook, R. R. Neumann, J. Henk, and I. Mertig
  Phys. Rev. B 100, 100401(R) (2019)  - DOI: 10.1103/PhysRevB.100.100401

• Electrical writing, deleting, reading, and moving of magnetic skyrmioniums in a racetrack device
  B. Göbel, A. F. Schäffer, J. Berakdar, I. Mertig, and S. S. P. Parkin
  Sci. Rep. 9, 12119 (2019)  - DOI: 10.1038/s41598-019-48617-z

• Spin and charge currents induced by the spin Hall and anomalous Hall effects upon crossing ferromagnetic/nonmagnetic interfaces
  A. Hönemann, C. Herschbach, D. V. Fedorov, M. Gradhand, and I. Mertig
  Phys. Rev. B 99, 024420 (2019)  - DOI: 10.1103/PhysRevB.99.024420