Martin Oltscher

Magnetoresistance oscillations induced by high-intensity terahertz radiation

We report on observation of pronounced terahertz radiation-induced magnetoresistivity oscillations in AlGaAs/GaAs two-dimensional electron systems, the terahertz analog of the microwave induced resistivity oscillations (MIRO). Applying high-power radiation of a pulsed molecular laser we demonstrate that MIRO, so far observed at low power only, are not destroyed even at very high intensities. Experiments with radiation intensity ranging over five orders of magnitude from 0.1 to

Deterministic transfer of spin polarization in wire-like lateral structures via the persistent spin helix

{10}^{4}\phantom{\rule{0.16em}{0ex}}{\mathrm{W}/\mathrm{cm}}^{2}

Gate-tunable large magnetoresistance in semiconductor-based spin valve devices (Conference Presentation)

reveal high-power saturation of the MIRO amplitude, which is well described by an empirical fit function

Gate-tunable large magnetoresistance in an all-semiconductor spin valve device

I/{(1+I/{I}_{s})}^{\ensuremath{\beta}}

Spin injection devices with high mobility 2DEG channels(Conference Presentation)

with

Electrical Spin Injection into High Mobility 2D Systems

\ensuremath{\beta}\ensuremath{\sim}1

Analog of microwave-induced resistance oscillations induced in GaAs heterostructures by terahertz radiation

. The saturation intensity

Hanle spin precession in a two-dimensional electron system

{I}_{s}

Optical investigation of electrical spin injection into an inverted two-dimensional electron gas structure

is of the order of tens of watts per square centimeter and increases by a factor of 6 by increasing the radiation frequency from 0.6 to 1.1 THz. The results are discussed in terms of microscopic mechanisms of MIRO and compared to nonlinear effects observed earlier at significantly lower excitation frequencies.

Gate-tunable large magnetoresistance in an all-semiconductor spin-transistor-like device

We used spatially- and time-resolved Kerr rotation microscopy to show that in lateral wire-like structures, based on a modulation-doped GaAs-AlGaAs quantum well, an optically initialized spin polarization can be deterministically transferred to specific lateral positions, employing the persistent spin helix (PSH). To this end, we show that confinement in two directions leads to a strong enhancement of the effective decay time of spin polarization, which can be exploited to transfer spin polarization over relatively large lateral distances. This is demonstrated by the investigation of L-shaped wire-like lateral structures, where the legs are positioned in directions parallel and perpendicular to the wave vector of the PSH.