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The anomalous Hall effect (AHE) is a fundamental spintronic charge-to-charge-current conversion phenomenon and closely related to spin-to-charge-current conversion by the spin Hall effect. Future h ...

A review on the recent development of intense laser-driven terahertz (THz) sources is provided here. The technologies discussed include various types of sources based on optical rectification (OR), spintronic emitters, and laser-filament-induced plasma. The emphasis is on OR using pump pulses with tilted intensity front. Illustrative examples of newly emerging applications are briefly discussed, in particular strong-field THz control of materials and acceleration and manipulation of charged particles.

Fundamental quantum optical processes in photogenerated excitons in Cu2O are demonstrated using few-cycle terahertz pulses and field-sensitive electro-optic sampling: (i) In a dilute ensemble of 3p excitons, stimulated terahertz emission from internal transitions to the energetically lower 2s state is observed at a photon energy of 6.6 meV, with a cross section of 10-14 cm2. (ii) An optically dark, dense, and cold 1s-paraexciton gas is prepared by two-photon generation of electron-hole pairs and subsequent phonon cooling. Intense multi-terahertz fields of order MV/cm coherently promote 70% of the quasiparticles from the 1s to the 2p state via a partial internal Rabi oscillation. Electro-optic detection monitors the Larmor precession of the Bloch vector directly in the time domain, with femtosecond resolution. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The optical properties of single-wall carbon nanotube sheets in the far-infrared have been investigated with THz time-domain spectroscopy. Over a wide frequency range from 1 THz to 40 THz, the complex dielectric function of the nanotube sample has been derived. Our data can be excellently reproduced by a Drude-Lorentz model function. The extracted fit parameters such as Lorentz resonance frequency and plasma frequency are consistent with values obtained by scanning tunneling techniques. We discuss the origin of both the Lorentz and Drude contribution in terms of direct and indirect optical transitions.

The relaxation mechanisms in magnetic thin films studied in all-optical pump probe experiments involve electrons, spin and lattice as well as the different couplings in between those. With this technique, the evolution of the electron and spin dynamics can be studied directly in real time from 100 fs to ns timescale. We give a comprehensive view of the current understanding of the processes involved. The details of the spin relaxation-mechanisms on the ultrafast and Landau-Lifshitz-Gilbert time scales are still unknown. Time-resolved reflectivity measurements on ferromagnetic transition metal films give an insight into the specific electronic and lattice relaxation processes. The time-resolved Kerr rotation measurements address the demagnetization and relaxation of the spin system. The demagnetization of the spin system observed in general is strongly coupled to the relaxation mechanism of the electrons, thus follows almost instantaneously the dynamics of the electron system. On the longer time scale, coherent magnetization dynamics is described by the Landau-Lifshitz-Gilbert equation and results in a precession with periods of 50 to 200 ps typical for ferromagnets. The full understanding of the mechanisms will be only accessible by a complete analysis of the interaction between electrons, lattice and spin system. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)