From the discovery to the control of THz spin currents Marco Battiato Institute of Solid State Physics Technical University, Vienna
Ultrafast demagnetization 1996: Discovery of ultrafast demagnetization [1] MO probe Ni Al Pump pulse [1] E. Beaurepaire et al., Phys. Rev. Lett. 76, 4250 (1996).
Ultrafast demagnetization 1ns Modern technology R&D 1ps 1fs
Ultrafast demagnetization 1ns Modern technology R&D 1ps Ultrafast magnetization dynamics 1fs
Ultrafast demagnetization Einstein - de Haas effect
Ultrafast demagnetization Angular momentum Phonons, orbital momentum, Spin system Some other system
Ultrafast demagnetization Spin system Angular momentum Ultrafast dissipation channel Phonons, orbital momentum, Some other system
Superdiffusive spin transport M. Battiato, K. Carva, P.M. Oppeneer, Phys. Rev. Lett. 105, 027203 (2010)
Femtosecond electron transport Dos E
Femtosecond electron transport Dos E
Femtosecond electron transport Dos E
Femtosecond electron transport v Dos E E
Femtosecond electron transport v Dos E E
Femtosecond electron transport v Dos E v 1nm/fs E
Femtosecond electron transport τ Dos E E v 1nm/fs τ tens of fs
Femtosecond electron transport τ tens of nm in tens of fs E Dos E v 1nm/fs τ tens of fs λ tens of nm
Electron cascade Dos E
Electron cascade Scattering with: phonon/impurity/defect electron Dos E
Electron cascade Scattering with phonon/impurity/defect Dos E
Electron cascade Scattering with another electron Dos E
Superdiffusive spin transport Boltzmann equation n(r,k,t) Transport Scattering Analytical integration n(z,e,t) M. Battiato, K. Carva, P.M. Oppeneer, Phys. Rev. Lett. 105, 027203 (2010)
Superdiffusive spin transport M. Battiato, K. Carva, P.M. Oppeneer, Phys. Rev. Lett. 105, 027203 (2010)
Why superdiffusion? Ballistic diffusion τ -> λ -> 15 nm Standard diffusion τ -> 0 λ -> 0 v -> v 1nm/fs τ 20 fs λ 20 nm New kinematic description required!
Superdiffusive spin transport E Dos
V. Zhukov, et al, Phys. Rev. B 73, 125105 (2006) Superdiffusive spin transport Energy (ev) Energy (ev)
Superdiffusive spin transport Ni Al Net spin current
Superdiffusive spin transport Ni Al 15nm [1] C. Stamm et al., Nature Mater. 6, 740 (2007).
Superdiffusive spin transport Ni Al M. Battiato, K. Carva, P.M. Oppeneer, Phys. Rev. Lett. 105, 027203 (2010)
Superdiffusive spin transport Ni Al M. Battiato, K. Carva, P.M. Oppeneer, Phys. Rev. Lett. 105, 027203 (2010)
Superdiffusive spin transport Ni Al M. Battiato, K. Carva, P.M. Oppeneer, Phys. Rev. Lett. 105, 027203 (2010)
Superdiffusive spin transport M. Battiato, K. Carva, P.M. Oppeneer, Phys. Rev. Lett. 105, 027203 (2010)
Ultrafast demagnetization in buried layers A. Eschenlor, MB et al, Nature Mater 12, 332 (2013).
Ultrafast demagnetization in buried layers Au capped Ni reference A. Eschenlor, MB et al, Nature Mater 12, 332 (2013).
Ultrafast demagnetization in buried layers Ni Al
Ultrafast demagnetization in buried layers Au Ni Al
Ultrafast demagnetization in buried layers Ni / Al Au / Ni / Al 4.0 mj/cm 2 absorbed fluence 4.8 mj/cm 2 absorbed fluence 4.0 mj/cm 2 absorbed fluence 6.3 mj/cm 2 absorbed fluence
Ultrafast magnetization increase Ni Fe Ru 1) Antiparallel 2) Parallel
Ultrafast magnetization increase [7] Element specific probe [8] D. Rudolf et al., Nat. Commun. 3, 1038 (2012)
Ultrafast magnetization increase 1) Antiparallel
Ultrafast magnetization increase 2) Parallel
Ultrafast magnetization increase 2) Parallel
Ultrafast magnetization increase 1) Antiparallel 2) Parallel
Ultrafast magnetization increase 1) Antiparallel 2) Parallel
Ultrafast magnetization increase 1) Antiparallel 2) Parallel D. Rudolf, MB et al. Nature Comm. 3, 1037 (2012).
THz spin currents shaping and contactless detection Direct control of temporal shape of THz spin current Ultrafast spin Ampere-meter Broadband THz emitter (covering the gap 5-10 THz) T. Kampfrath, MB et al. Nature Nonotech. 8, 256 (2013).
Verified predictions Ultrafast demagnetization in metals only Saturation of demagnetization at high fluences Timescale of demagnetization Experimentally observed spin transfer Only driver? Demagnetization of thin metals on insulators predicted to be negligible
Conclusions and outlook Microscopical mechanism of the ultrafast demagnetization Possibility of transport of spin information in the fs timescale Opens the route to fs spinelectronics
Thanks to K. Carva P. Maldonado P. M. Oppeneer D. Rudolf C. La-O-Vorakiat R. Adam J. M. Shaw E. Turgut A. Eschenlohr N. Pontius T. Kachel K. Holldack S. Mathias P. Grychtol H. T. Nembach T. J. Silva M. Aeschlimann R. Mitzner A. Föhlisch C. Stamm H. C. Kapteyn M. M. Murnane C. M. Schneider Thank you for your attention