Abstract-Strong Coupling of Epsilon-Near-Zero Phonon Polaritons in Polar Dielectric Heterostructures

Nikolai Christian Passler, Christopher R. Gubbin, Thomas Folland, I. Razdolski, D. Scott Katzer, D. F. Storm, Martin Wolf, Simone De Liberato, Joshua D Caldwell, Alexander Paarmann,

https://cdn-pubs.acs.org/doi/10.1021/acs.nanolett.8b01273

We report the first observation of epsilon near zero (ENZ) phonon polaritons in an ultrathin AlN film fully hybridized with surface phonon polaritons (SPhP) supported by the adjacent SiC substrate. Employing a strong coupling model for the analysis of the dispersion and electric field distribution in these hybridized modes, we show that they share the most prominent features of the two precursor modes. The novel ENZ-SPhP coupled polaritons with a highly propagative character and deeply sub-wavelength light confinement can be utilized as building blocks for future infrared and terahertz (THz) nanophotonic integration and communication devices.

Abstract-Surface plasmon-mediated nanoscale localization of laser-driven sub-THz spin dynamics in magnetic dielectrics

Alexander Chekhov, Alexander I. Stognij, T. Satoh, Tatiana V. Murzina, I. Razdolski, Andrzej Stupakiewicz,

https://pubs.acs.org/doi/abs/10.1021/acs.nanolett.8b00416?journalCode=nalefd

We report spatial localization of the effective magnetic field generated via the inverse Faraday effect employing surface plasmon polaritons (SPPs) at a hybrid Au/rare-earth iron garnet interface. Analyzing, both numerically and analytically, the electric field of the SPPs at a hybrid interface, we corroborate our study with a proof-of-concept experiment showing efficient SPP-driven excitation of coherent spin precession with a 0.41 THz frequency. We argue that the sub-diffractional confinement of the SPP electric field enables strong spatial localization of the SPP-mediated excitation of spin dynamics. We demonstrate a two orders of magnitude enhancement of the excitation efficiency at the surface plasmon resonance within a 100 nm layer of a dielectric garnet. Our findings broaden the horizons of ultrafast spin-plasmonics and open pathways towards non-thermal opto-magnetic recording on the nanoscale.

Abstract-Launching magnons at the terahertz speed of the spin Seebeck effect

T. Seifert, S. Jaiswal, J. Barker, I. Razdolski, J. Cramer, O. Gueckstock, S. Watanabe, C. Ciccarelli, A. Melnikov, G. Jakob, S.T.B. Goennenwein, G. Woltersdorf, P.W. Brouwer, M. Wolf, M. Kläui, T. Kampfrath

(Submitted on 3 Sep 2017)

https://arxiv.org/abs/1709.00768

Transport of spin angular momentum is an essential operation in spintronic devices. In magnetic insulators, spin currents are carried by magnons and can be launched straightforwardly by heating an adjacent metal layer. Here, we study the ultimate speed of this spin Seebeck effect with 10-fs time resolution in prototypical bilayers of ferrimagnetic yttrium iron garnet and platinum. Upon exciting the metal by a laser pulse, the spin flow is measured using the inverse spin Hall effect and terahertz electrooptic sampling. The spin Seebeck current reaches its peak within ~200 fs, a hallmark of the photoexcited metal electrons approaching a Fermi-Dirac distribution. Analytical modeling shows the spin Seebeck response is virtually instantaneous because the ferrimagnetic spins react without inertia and the metal spins impinging on the interface have a correlation time of only ~4 fs. Novel applications for material characterization, interface probing, spin-noise detection and terahertz spin pumping emerge.

Abstract-Terahertz dynamics of spins and charges in CoFe/Al2O3 multilayers

J. D. Costa, T. J. Huisman, R. V. Mikhaylovskiy, I. Razdolski, J. Ventura, J. M. Teixeira, D. S. Schmool, G. N. Kakazei, S. Cardoso, P. P. Freitas, Th. Rasing, and A. V. Kimel

Phys. Rev. B 91, 104407 – Published 12 March 2015

https://journals.aps.org/prb/abstract/10.1103/PhysRevB.91.104407

The ultrafast laser-induced response of spins and charges in CoFe/Al2O3 multilayers are studied using THz and optical pump-probe spectroscopies. We demonstrate the possibility of ultrafast manipulation of the transport and magnetic properties of the multilayers with femtosecond laser excitation. In particular, using time-resolved THz transmission experiments we found that such an excitation leads to a rapid increase of the THz transmission (i.e., electric resistivity). Our experiments also reveal that femtosecond laser excitation results in the emission of broadband THz radiation. To reveal the origin of the emitted THz radiation, we performed magnetic-dependent measurements of the THz emission. We also compared the observed electric field of the THz radiation to calculations performed using subpicosecond laser-induced demagnetization measurements. The good agreement between the experimentally obtained spectra and the calculations corroborates that the measured THz emission originates from the demagnetization process.

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