Giant magneto-optical faraday effect in HgTe thin films in the terahertz spectral range.

We report the observation of a giant Faraday effect, using terahertz (THz) spectroscopy on epitaxial HgTe thin films at room temperature. The effect is caused by the combination of the unique band structure and the very high electron mobility of HgTe. Our observations suggest that HgTe is a high-potential material for applications as optical isolator and modulator in the THz spectral range.

Magnetic and magnetoelectric excitations in multiferroic manganites.

We review the recent experimental findings concerning the magnetic and magnetoelectric excitations in multiferroic manganites with special focus on orthorhombic RMnO(3) (R = rare earth). The dynamics of these materials has attracted special attention recently due to the existence of novel magnetoelectric excitations which were termed electromagnons. In addition to the strong electric activity of the electromagnons, a series of other excitations of magnetic and magnetoelectric nature is observed in the same frequency range as the electromagnons. We summarize the systematics of the existing modes and the current understanding of the underlying mechanisms.

Evidence for electroactive excitation of the spin cycloid in TbMnO3.

Terahertz electromagnetic excitations in the multiferroic TbMnO3 single crystals are investigated across the magnetic field induced rotation of the magnetic spin cycloid. In addition to the electromagnon along the a axis, the detailed polarization analysis of the experimental spectra suggests the existence of an electroactive excitation for ac electric fields of the electromagnetic wave along the crystallographic c axis. This excitation is possibly the electroactive eigenmode of the spin-cycloid in TbMnO3, which has been predicted within the inverse Dzyaloshinskii-Moriya mechanism of magnetoelectric coupling.