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Topological insulators are characterized by Dirac cone surface states with electron spins aligned in the surface plane and perpendicular to their momenta. Recent theoretical and experimental work implied that this specific spin texture…
We report on the observation of photogalvanic effects in epitaxially grown Sb_2Te_3 three-dimensional (3D) topological insulators (TI). We show that asymmetric scattering of Dirac electrons driven back and forth by the terahertz electric…
The generation of photocurrent in condensed matter is of main interest for photovoltaic and optoelectronic applications. Shift current, a nonlinear photoresponse, has attracted recent intensive attention as a dominant player of bulk…
Using THz spectroscopy in external magnetic fields we investigate the low-temperature charge dynamics of strained HgTe, a three dimensional topological insulator. From the Faraday rotation angle and ellipticity a complete characterization…
Nonlinear couplings between photons and electrons in new materials give rise to a wealth of interesting nonlinear phenomena. This includes frequency mixing, optical rectification or nonlinear current generation, which are of particular…
Topological insulators are innovative materials with semiconducting bulk together with surface states forming a Dirac cone, which ensure metallic conduction in the surface plane. Therefore, topological insulators represent an ideal platform…
Topological Insulator-based devices can transport electrons/photons at the surfaces of materials without any back reflections, even in the presence of obstacles. Topological properties have recently been studied using non-reciprocal…
Topological insulators represent a novel state of matter with surface charge carriers having a massless Dirac dispersion and locked helical spin polarization. Many exciting experiments have been proposed by theory, yet, their execution have…
We report on the systematic study of infrared/terahertz spectra of photocurrents in (Bi,Sb)Te based three dimensional topological insulators. We demonstrate that in a wide range of frequencies, ranging from fractions up to tens of…
We theoretically study spin and charge transport induced by a twisted light beam irradiated on a disordered surface of a doped three dimensional topological insulator (TI). We find that various types of spin vortices are imprinted on the…
We report on time-resolved ultrafast optical spectroscopy study of the topological insulator (TI) Bi$_2$Se$_3$. We unravel that a net spin polarization can not only be generated using circularly polarized light via interband transitions…
Topological insulators (TIs) represent a novel quantum state of matter, characterized by edge or surface-states, showing up on the topological character of the bulk wave functions. Allowing electrons to move along their surface, but not…
We report on terahertz (THz) radiation under electrical pumping from a degenerate semiconductor possessing an electron accumulation layer. In InN, the random grating formed by topographical defects provides high-efficiency coupling of…
Several recent experiments on three-dimensional topological insulators claim to observe a large charge current-induced non-equilibrium ensemble spin polarization of electrons in the helical surface state. We present a comprehensive…
Topological insulators have surface states with a remarkable helical spin structure, with promising prospects for applications in spintronics. Strategies for generating spin polarized currents, such as the use of magnetic contacts and…
A three-dimensional topological insulator manifests gapless surface modes, described by two-dimensional Dirac equation. We study magnetic textures, such as domain walls and vortices, in a ferromagnetic thin film deposited on a…
Three-dimensional topological insulators (TIs) are characterized by spin-polarized Dirac-cone surface states that are protected from backscattering by time-reversal symmetry. Control of the spin polarization of topological surface states…
We theoretically study the electric current induced by the temporally oscillating magnetic field onto a three-dimensional topological insulator based on the linear response theory. The electric current flows on its surface because of the…
The terahertz radiation-induced conductivity and dielectric polarization tensors as well as the Faraday and Kerr rotation angles and the non-equilibrium spin textures are studied for two-dimensional electron gas with strong spin-orbit…
The recent discovery of topology-protected charge transport of ultimate thinness on surfaces of three-dimensional topological insulators (TIs) are breaking new ground in fundamental quantum science and transformative technology. Yet a…