arXiv subjects

S. A. Tarasenko

Publications and source records attributed to S. A. Tarasenko.

At least 91 records · Page 5Linked to original sources

arXiv2007

Electron scattering in quantum wells subjected to an in-plane magnetic field

It is shown that the electron scattering by static defects, acoustic or optical phonons in quantum wells subjected to an in-plane magnetic field is asymmetric. The probability of scattering contains terms which are proportional to both the electron wave vector and the magnetic field components. The terms under study are caused by the lack of an inversion center in quantum wells due to structure or bulk inversion asymmetry although they are of pure diamagnetic origin. Such a magnetic field induced asymmetry of scattering can be responsible for a number of phenomena. In particular, the asymmetry of inelastic electron-phonon interaction leads to an electric current flow if only the electron gas is driven out of thermal equilibrium with the crystal lattice.

cond-mat.mes-hall↗

arXiv2007

Photogalvanic effects in HgTe quantum wells

We report on the observation of the terahertz radiation induced circular (CPGE) and linear (LPGE) photogalvanic effects in HgTe quantum wells. The current response is well described by the phenomenological theory of CPGE and LPGE.

cond-mat.mes-hall↗

arXiv2007

Magneto-gyrotropic photogalvanic effects due to inter-subband absorption in quantum wells

We report on the observation of the magneto-photogalvanic effect (MPGE) due to inter-subband transitions in (001)-oriented GaAs quantum wells. This effect is related to the gyrotropic properties of the structures. It is shown that inter-subband absorption of linearly polarized radiation may lead to spin-related as well as spin independent photocurrents if an external magnetic field is applied in the plane of the quantum well. The experimental results are analyzed in terms of the phenomenological theory and microscopic models of MPGE based on either asymmetric optical excitation or asymmetric relaxation of carriers in k-space. We observed resonant photocurrents not only at oblique incidence of radiation but also at normal incidence demonstrating that conventionally applied selection rules for the inter-subband optical transitions are not rigorous.

cond-mat.mtrl-sci↗

arXiv2007

Intervalley scattering and weak localization in Si-based two-dimensional structures

We have measured the weak localization magnetoresistance in (001)-oriented Si MOS structures with a wide range of mobilities. For the quantitative analysis of the data, we have extended the theory of weak-localization corrections in the ballistic regime to the system with two equivalent valleys in electron spectrum. This theory describes the observed magnetoresistance and allows the extraction of the phase breaking time tau_phi and the intervalley scattering time tau_v. The temperature dependences tau_phi(T) for all studied structures are in good agreement with the theory of electron-electron interaction effects in two-dimensional systems. The intervalley scattering is elastic and rather strong: tau_v is typically only an order of magnitude greater than the transport time, tau. It is found that the intervalley scattering rate is temperature-independent and the ratio tau_v/tau decreases with increasing the electron density. These observations suggest that the roughness of the Si-SiO2 interface plays the major role in intervalley scattering.

cond-mat.dis-nn↗

arXiv2007

Orbital mechanism of the circular photogalvanic effect in quantum wells

It is shown that the free-carrier (Drude) absorption of circularly polarized radiation in quantum well structures leads to an electric current flow. The photocurrent reverses its direction upon switching the light helicity. A pure orbital mechanism of such a circular photogalvanic effect is proposed that is based on interference of different pathways contributing to the light absorption. Calculation shows that the magnitude of the helicity dependent photocurrent in $n$-doped quantum well structures corresponds to recent experimental observations.

cond-mat.mes-hall↗

arXiv2006

Pure spin currents induced by spin-dependent scattering processes in SiGe quantum well structures

We show that spin-dependent electron-phonon interaction in the energy relaxation of a two-dimensional electron gas results in equal and oppositely directed currents in the spin-up and spin-down subbands yielding a pure spin current. In our experiments on SiGe heterostructures the pure spin current is converted into an electric current applying a magnetic field that lifts the cancellation of the two partial charge flows. A microscopic theory of this effect, taking account of the asymmetry of the relaxation process, is developed being in a good agreement with the experimental data.

cond-mat.mes-hall↗

arXiv2006

Spin photocurrents and circular photon drag effect in (110)-grown quantum well structures

We report on the study of spin photocurrents in (110)-grown quantum well structures. Investigated effects comprise the circular photogalvanic effect and so far not observed circular photon drag effect. The experimental data can be described by an analytical expression derived from a phenomenological theory. A microscopic model of the circular photon drag effect is developed demonstrating that the generated current has spin dependent origin.

cond-mat.mes-hall↗

arXiv2006

Spin orientation and spin currents induced by linearly polarized light

To date, optical orientation of free-carrier spins and spin currents have been achieved by circularly polarized light, while the linearly polarized light has been used for optical alignment of electron momenta. Here we show that, in low-dimensional structures, absorption of the linearly polarized light also leads to the spin polarization and spin photocurrent, and, thus, the electron and hole spins can be manipulated by light of zero helicity. The microscopic description of the both effects is developed for interband optical transitions in undoped quantum wells (QWs) as well as for direct intersubband and indirect intrasubband (Drude-like) transitions in $n$-doped QW structures.

cond-mat.mes-hall↗

arXiv2006

Scattering induced spin orientation and spin currents in gyrotropic structures

It is shown that additional contributions both to current-induced spin orientation and to the spin Hall effect arise in quantum wells due to gyrotropy of the structures. Microscopically, they are related to basic properties of gyrotropic systems, namely, linear in the wave vector terms in the matrix element of electron scattering and in the energy spectrum. Calculation shows that in high-mobility structures the contribution to the spin Hall current considered here can exceed the term originated from the Mott skew scattering.

cond-mat.mes-hall↗

arXiv2006

Spin orientation of a two-dimensional electron gas by a high-frequency electric field

Coupling of spin states and space motion of conduction electrons due to spin-orbit interaction opens up possibilities for manipulation of the electron spins by electrical means. It is shown here that spin orientation of a two-dimensional electron gas can be achieved by excitation of the carriers with a linearly polarized high-frequency electric field. In (001)-grown quantum well structures excitation with in-plane ac electric field induces orientation of the electron spins along the quantum well normal, with the spin sign and the magnitude depending on the field polarization.

cond-mat.mes-hall↗

arXiv2005

Optical orientation of electron spins by linearly polarized light

Absorption of circularly polarized light in semiconductors is known to result in optical orientation of electron and hole spins. It has been shown here that in semiconductor quantum well structures spin orientation of carriers can be achieved by linearly or even unpolarized light. Moreover, the sign and magnitude of the spin orientation can be varied by rotating the polarization plane of incidence light. The effect under study is related to reduced symmetry of the quantum wells as compared to bulk materials and, microscopically, caused by zero-field spin splitting of electron and hole states.

cond-mat.mes-hall↗

arXiv2005

Magneto-Gyrotropic Photogalvanic Effects in Semiconductor Quantum Wells

We show that free-carrier (Drude) absorption of both polarized and unpolarized terahertz radiation in quantum well (QW) structures causes an electric photocurrent in the presence of an in-plane magnetic field. Experimental and theoretical analysis evidences that the observed photocurrents are spin-dependent and related to the gyrotropy of the QWs. Microscopic models for the photogalvanic effects in QWs based on asymmetry of photoexcitation and relaxation processes are proposed. In most of the investigated structures the observed magneto-induced photocurrents are caused by spin-dependent relaxation of non-equilibrium carriers.

cond-mat.mes-hall↗

arXiv2005

Pure spin photocurrents in low-dimensional structures

As is well known the absorption of circularly polarized light in semiconductors results in optical orientation of electron spins and helicity-dependent electric photocurrent, and the absorption of linearly polarized light is accompanied by optical alignment of electron momenta. Here we show that the absorption of unpolarized light leads to generation of a pure spin current, although both the average electron spin and electric current vanish. We demonstrate this for direct interband and intersubband as well as indirect intraband (Drude-like) optical transitions in semiconductor quantum wells (QWs).

cond-mat.mes-hall↗

arXiv2005

Photo-induced pure spin currents in quantum wells

As is well known the absorption of circularly polarized light in semiconductors results in optical orientation of electron spins and helicity-dependent electric photocurrent, and the absorption of linearly polarized light is accompanied by optical alignment of electron momenta. Here we show that the absorption of unpolarized light in a quantum well (QW) leads to generation of a pure spin current, although both the average electron spin and electric current are vanishing.

cond-mat.mes-hall↗

arXiv2004

Suppression of spin beats in magneto-oscillation phenomena in two-dimensional electron gas

Theory of magneto-oscillation phenomena has been developed for two-dimensional electron systems with linear-in-k spin splitting. Both Dresselhaus and Rashba contributions are taken into account. It has been shown that the pattern of the magneto-oscillations depends drastically on the ratio between the above terms. The presence of only one type of the k-linear terms gives rise to the beats, i.e. two close harmonics corresponding to the spin-split subbands. However, if the strengths of both contributions are comparable, the third (central) harmonics appears in the spectrum of the magneto-oscillations. For equal strengths of the contributions, only the central harmonic survives, and the oscillations occur at a single frequency, although the k-linear terms remain in the Hamiltonian. Such suppression of the spin beats is studied in detail by the example of the Shubnikov-de Haas effect.

cond-mat.mes-hall↗

arXiv2004

Spin-dependent resonant tunneling in symmetrical double-barrier structure

A theory of resonant spin-dependent tunneling has been developed for symmetrical double-barrier structures grown of non-centrosymmetrical semiconductors. The dependence of the tunneling transparency on the spin orientation and the wave vector of electrons leads to (i) spin polarization of the transmitted carriers in an in-plane electric field, (ii) generation of an in-plane electric current under tunneling of spin-polarized carriers. These effects originated from spin-orbit coupling-induced splitting of the resonant level have been considered for double-barrier tunneling structures.

cond-mat.mes-hall↗

arXiv2004

Spin injection and detection by resonant tunneling structure

A theory of spin-dependent electron transmission through resonant tunneling diode (RTD) grown of non-centrosymmetrical semiconductor compounds has been presented. It has been shown that RTD can be employed for injection and detection of spin-polarized carriers: (i) electric current flow in the interface plane leads to spin polarization of the transmitted carriers, (ii) transmission of the spin-polarized carriers through the RTD is accompanied by generation of an in-plane electric current. The microscopic origin of the effects is the spin-orbit coupling-induced splitting of the resonant level.

cond-mat.mes-hall↗

arXiv2003

Magneto-Gyrotropic Photogalvanic Effect in Semiconductor Quantum Wells

We investigate both experimentally and theoretically, the magneto-gyrotropic photogalvanic effect in zinc-blende based quantum wells with $C_{2v}$ point-group symmetry using optical excitation in the terahertz frequency range. The investigated frequencies cause intra-subband but no inter-band and inter-subband transitions. While at normal incidence the photocurrent vanishes at zero magnetic field, it is shown that an in-plane magnetic field generates photocurrents both for polarized and unpolarized excitation. In general the spin-galvanic effect, caused by circularly polarized light, and the magneto-gyrotropic effect, caused by unpolarized excitation, is superimposed. It is shown that in the case of two specific geometries both effects are separable.

cond-mat↗