Photogalvanic current in a double quantum well

A double quantum well affected by external alternating electric field with in- and out-of-plane components is studied. This field causes transitions between near-degenerate states located in different wells. The phototransitions are accompanied by the in-plane momentum nonconservation caused by the impurity scattering. We study the in-plane stationary current due to the lack of the in-plane symmetry of these indirect phototransitions. It is shown that the value and direction of the current are determined by the polarization of light. The linear and circular photogalvanic coefficients are found. When the photon energy approaches the distance between subbands these coefficients have their symmetric and antisymmetric resonance behaviors, respectively.     

Photogalvanic current in electron gas over a liquid helium surface

We study the stationary surface photocurrent in 2D electron gas near the helium surface. Electron gas is assumed to be attracted to the helium surface due to the image attracting force and an external stationary electric field. The alternating electric field has both vertical and in-plane components. The photogalvanic effect originates from the periodic transitions of electrons between quantum subbands in the vertical direction caused by a normal component of the alternating electric field accompanied by synchronous in-plane acceleration/deceleration due to the electric field in-plane component. The effect needs vertical asymmetry of the system. The problem is considered taking into account a friction caused by the electron-ripplon interaction. The photocurrent resonantly depends on the field frequency. The resonance occurs at field frequencies close to the distance between well subbands. The resonance is symmetric or antisymmetric depending on the kind (linear or circular) of polarization.     

Intraminiband plasmons in a superlattice within a parabolic well

A well defined collective plasma resonance corresponding to electrons tunneling back and forth through superlattice barriers is observed in a series of modulation doped AlGaAs heterostructures containing a superlattice within a parabolic potential. Due to occupation of a large fraction of the miniband, the resonance frequency decreases strongly with increasing superlattice barrier thickness.     

Infrared absorption in parabolic multiquantum well structures

The absorption constant for intraband transitions in parabolic multiquantum well structures is calculated and compared with intraband absorption in a square well superlattice. The parabolic multiple quantum well structure may be used as an Infrared detector with the possibility of lower leakage current compared to one made of square wells.     

Impurity optical absorption in parabolic quantum well

Optical absorption in GaAs parabolic quantum well in the presence of hydrogenic impurity is considered. The absorption coefficient associated with the transitions between the upper valence subband and donor ground state is calculated. The impurity ground state wave function and energy are obtained using the variational method. Dependence of the absorption spectra on impurity position in quantum well was investigated. It is shown, that along with quantum well width decrease the absorption threshold shifts to higher frequencies. Results obtained within frames of parabolic approximation are compared with results for rectangular infinite-barrier quantum well case. The acceptor state → conduction band transitions considered as well.     

The quantum acoustomagnetoelectric field in a quantum well with a parabolic potential

The acoustomagnetoelectric (AME) field in a quantum well with a parabolic potential (QWPP) has been studied in the presence of an external magnetic field. The analytic expression for the AME field in the QWPP is obtained by using the quantum kinetic equation for the distribution function of electrons interacting with external phonons. The dependence of the AME field on the temperature T of the system, the wavenumber q of the acoustic wave and external magnetic field B for the specific AlAs/GaAs/AlAs is achieved by using a numerical method. The problem is considered for both cases: The weak magnetic field region and the quantized magnetic field region. The results are compared with those for normal bulk semiconductor and superlattices to show the differences, and we use the quantum theory to calculate the AME field in the QWPP.     

Self-channelling of electric current in a quantum well

We have directly demonstrated that homogeneous photoexcitation of a quantum well in presence of uniform tilted magnetic field gives rise to a set of bypass in-plane electric currents of a different value which may flow even in the opposite directions simultaneously. The effect has been observed in an asymmetric InAs quantum well under the Landau quantization. Theoretical model of the effect are discussed as well as the related problems.     

单量子阱的自旋电流

利用密度矩阵的方法,由多粒子体系的薛定谔方程得到了微观体系中电子输运的概率方程，由此推出了单量子阱的自旋电流和电荷流的表达式.研究发现，在某种条件下单量子阱中只存在自旋电流；同时还给出了左右自旋电流之间的关系.结果表明:当单量子阱中的电子发生自旋共振时,自旋电流出现极大值并且随着自旋退相干时间的减小而减小. 关键词： 自旋共振 自旋电流     

Photogalvanic effects in topological insulators

We discuss optical absorption in topological insulators and study possible photoelectric effects theoretically. We found that absorption of circularly polarized electromagnetic waves in two-dimensional topological insulators results in electric current in the conducting 1D edge channels, the direction of the current being determined by the light polarization. We suggest two ways of inducing such a current: due to magnetic dipole electron transitions stimulated by irradiation of frequency below the bulk energy gap, and due to electric dipole transitions in the bulk at frequencies larger than the energy gap with subsequent capture of the photogenerated carriers on conducting edge states.     

Photogalvanic effects in heteropolar nanotubes

We show that an electrical shift current is generated when electrons are photoexcited from the valence to conduction bands on a BN nanotube. This photocurrent follows the light pulse envelope and its symmetry is controlled by the atomic structure of the nanotube. We find that the shift current has an intrinsic quantum mechanical signature in which the chiral index of the tube determines the direction of the current along the tube axis. We identify the discrete lattice effects in the tangent plane of the tube that lead to an azimuthal component of the shift current. The nanotube shift current can lead to ultrafast optoelectronic and optomechanical applications.     

Photogalvanic effect in ferromagnets with a noncoplanar magnetization distribution

The photogalvanic effect in ferromagnetic materials is predicted. This is the appearance of the direct electric current in a ferromagnet sample due to a high-frequency alternating electric field. The phenomenological theory of this photogalvanic effect in ferromagnets is developed and the simplest microscopic model explaining the occurrence of the photogalvanic effect in a medium with the helical magnetic structure is proposed. The photogalvanic effect arises owing to the breaking of the symmetry with respect to the reversal of the electron motion in the medium with a noncoplanar magnetization distribution.