A5059000774- Quantum and electron transport phenomena
- Semiconductor Quantum Structures and Devices
- Terahertz technology and applications
- Magnetic properties of thin films
- Atomic and Subatomic Physics Research
- Topological Materials and Phenomena
- Advancements in Semiconductor Devices and Circuit Design
- Photonic and Optical Devices
- Photonic Crystals and Applications
- Magnetic and transport properties of perovskites and related materials
- Characterization and Applications of Magnetic Nanoparticles
- Functional Brain Connectivity Studies
- Electrical and Bioimpedance Tomography
Leibniz Institute of Photonic Technology
2017-2020
Physikalisch-Technische Bundesanstalt
2013-2018
Universidade Estadual de Campinas (UNICAMP)
1991
We induce ultrafast magneto-photocurrents in a GaAs crystal employing interband excitation with femtosecond laser pulses at room temperature and non-invasively separate surface bulk contributions to the overall current response. The separation between different symmetry is achieved by measuring simultaneously emitted terahertz radiation for sample orientations. Excitation intensity photon energy dependences of linearly circularly polarized excitations reveal an involvement microscopic...
Abstract Spatial quantitative information about magnetic nanoparticle (MNP) distributions is a prerequisite for biomedical applications like hyperthermia and drug targeting. This can be gathered by means of magnetorelaxometry (MRX) imaging, where the relaxation previously aligned MNP’s moments measured sensitive magnetometers an inverse problem solved. To remove or minimize shielding in which MRX imaging carried out today, knowledge influence background fields on prerequisite. We show...
We have performed a series of photoreflectance measurements in modulation-doped AlGaAs/GaAs heterojunction containing high mobility two-dimensional electron gas. Measurements were as function temperature the range 2 K≤T≤300 K. studied Franz–Keldysh oscillations associated with E0 transition both GaAs and AlGaAs. The fields obtained from these for sides are quite different. Also, dependence radically In fact, field side sample is very similar to that single undoped film deposited on...
Abstract The anomalous Hall (AH) and spin effects are important tools for the generation, control, detection of spin-polarized currents in solids and, thus, hold promises future spintronic applications. Despite tremendous work on these effects, their ultrafast dynamic response is still not well explored. Here, we induce AH a magnetically-biased semiconductor by optical femtosecond excitation at room temperature. currents’ dynamics studied detecting simultaneously emitted THz radiation. We...
We generate ultrafast magneto-photocurrents in bulk GaAs and non-invasively separate surface contributions to the overall current. This method enables investigation of processes such as anisotropic-distribution relaxation inverse Spin Hall effect.
Using a microscopic theory that combines k.p band structure calculations with multisubband semiconductor Bloch equations we are capable of computing coherent optically-induced rectification, injection, and shift currents in semiconductors nanostructures. A 14-band has been employed to obtain electron states non-centrosymmetric systems. Numerical solutions the provide detailed transparent description dynamics material excitations terms interband intersubband polarizations/coherences...
Purpose The purpose of this paper is to present a simulation study using model new optically pumped magnetometer sensor for application in the field magnetoencephalography. effects distance and orientation on measurement information sensitivity neuronal sources are investigated. Further, uses combinatorial optimization approach placement measure spontaneous activity region occipital cortex. Design/methodology/approach This studies cortical information. A three-compartment head, boundary...
We induce ultrafast photocurrents in a GaAs crystal exposed to magnetic field by optical femtosecond excitation. The magneto-photocurrents are studied time-resolved detection of the simultaneously emitted THz radiation. find that their dynamics differ considerably from other which expected follow temporal shape intensity. attribute this difference influence carrier-anisotropy relaxation on magneto-photocurrents. Our measurements show anisotropy for carrier densities ranging between $10^{16}$...
We study THz radiation from magneto-optically induced ultrafast currents in GaAs. Magnetic field and excitation intensity are found to have a distinct influence on the shape of traces. The results suggest that these an appropriate tool investigate k-space carrier dynamics semiconductors.
We study THz emission from magneto-optically induced ultrafast photocurrents in a GaAs crystal. Analyzing currents appearing the direction of externally applied magnetic field, we observe different current dynamics for linearly- and circularly-polarized excitation.
The anomalous velocity causes spin-polarized carriers to move perpendicular an electric or parallel a magnetic driving field. It is at the origin of spin Hall and effects. Here, we employ time-domain THz spectroscopy study effect, both which are optically induced in GaAs, on sub-picosecond time scale. Our results not only enable distinction between intrinsic (Berry curvature) extrinsic (scattering) effects but also demonstrate inversion currents versus excitation photon energy.