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排序方式: 共有162条查询结果,搜索用时 31 毫秒
101.
Greilich A Oulton R Zhukov EA Yugova IA Yakovlev DR Bayer M Shabaev A Efros AL Merkulov IA Stavarache V Reuter D Wieck A 《Physical review letters》2006,96(22):227401
Electron spin coherence has been generated optically in n-type modulation doped (In,Ga)As/GaAs quantum dots (QDs) which contain on average a single electron per dot. The coherence arises from resonant excitation of the QDs by circularly polarized laser pulses, creating a coherent superposition of an electron and a trion. Time dependent Faraday rotation is used to probe the spin precession of the optically oriented electrons about a transverse magnetic field. The coherence generation can be controlled by pulse intensity, being most efficient for (2n+1)pi pulses. 相似文献
102.
The magnetic field-induced splitting of the ground-state spin levels of an acceptor center, described by superposition of
the Coulomb and the central-cell potentials, has been calculated for diamond-type. An analytic expression for the g factor obtained in the zero-radius potential approximation depends only on the light to heavy hole mass ratio. It is shown
that the differences between the values of the g factor for the limiting cases of purely Coulomb and zero-radius potentials do not exceed 5%, thus permitting one to use this
analytic expression for estimates.
Fiz. Tverd. Tela (St. Petersburg) 39, 58–60 (January 1997) 相似文献
103.
Letters in Mathematical Physics - We introduce a new category of differential graded multi-oriented props whose representations (called homotopy algebras with branes) in a graded vector... 相似文献
104.
I. A. Merkulov K. V. Kavokin G. Mackh B. Kuhn-Heinrich W. Ossau A. Waag G. Landwehr D. R. Yakovlev 《Physics of the Solid State》1997,39(11):1859-1863
An experimental and theoretical study of the magnetic polaron states of two-dimensional excitons in quantum wells based on
semimagnetic semiconductors (Cd,Mn)Te is reported. It is shown that magnetic-polaron formation in in-plane magnetic fields
leads to a lowering of the system symmetry, provided the fields are not too strong. The magnetic moment of the polaron thus
formed is not parallel to the external magnetic field and contains a component normal to the quantum-well plane. This spontaneous
lowering of the symmetry results in a change of the polarization characteristics of the luminescence from magnetic polaron
states and in a weakening (compared to the three-dimensional case) in the efficiency of magnetic field-induced polaron suppression.
Fiz. Tverd. Tela (St. Petersburg) 39, 2079–2084 (November 1997) 相似文献
105.
The energy distribution between different types of seismic waves produced by a source of longitudinal and transverse waves with an arbitrary radiation pattern in an elastic half-space is considered. With an appropriate choice of the angular distribution functions, this source can model an earthquake source. A direct theoretical comparison of the energy distributions of seismic waves generated by an underground explosion and an earthquake is carried out. Analytical relationships that describe the dependence of the energy distribution between different types of waves on the parameters of the medium and the source are derived. 相似文献
106.
Buoyancy driven flows of two Bingham fluids in an inclined ductare considered, providing a simplified model for many oilfieldcementing processes. The flows studied are near-uniaxial andstratified, with the heavy fluid moving down the incline, displacingthe lighter fluid upwards. Existence and uniqueness resultsare obtained for quite general flows and for those which satisfyan axial flow rate constraint. Parametric dependence of thesolutions on the axial pressure gradient is studied. Flows whichsatisfy a zero net axial flow constraint result from an axialpressure gradient which minimizes the viscous dissipation, butnot the plastic dissipation. A regularization method is usedto compute solutions to these problems for (more or less) arbitraryfluid-fluid interfaces and duct-cross sections. Examples relatedto a number of practical applications are presented. 相似文献
107.
Spin-orbit splitting, strain-potential constants, and the g factor of the acceptor-center ground state described by a superposition of a Coulomb and a central-cell potential have been
calculated for wide-band-gap semiconductors, such as GaN. Analytical expressions for these parameters, which depend only on
the light-to heavy-hole mass ratio, have been obtained within the zero-range potential model. It is shown that the differences
between these parameters for the limiting cases of purely Coulomb and zero-range potentials do not exceed 7%, thus permitting
one to use for estimates simple analytical expressions. Calculation of the acceptor-center ground state made for the hexagonal
modification of GaN suggests a strong anisotropy of the g factor, whereas measurements yield a practically isotropic value of g close to that of a free electron. This contradiction is removed if a spontaneous strain due to the Jahn-Teller effect appears
perpendicular to the C
6 axis of the crystal near the acceptor center.
Fiz. Tverd. Tela (St. Petersburg) 40, 1002–1009 (June 1998) 相似文献
108.
Specific features in the behavior of localized magnetic polarons formed under optical excitation in heterostructures based
on semimagnetic semiconductors are considered. These features are due to the strong anisotropy of the hole g factor in low-dimensional systems based on zincblende crystals. The anisotropy is due to the strong spin-orbit coupling in
the valence band which, in quantum confinement conditions, results in quadrupole splitting of the hole spin levels. The g factor anisotropy manifests itself in a strong anisotropy of the magnetic and magneto-optical characteristics of localized
magnetic polarons.
Fiz. Tverd. Tela (St. Petersburg) 40, 800–802 (May 1998) 相似文献
109.
110.
Oulton R Greilich A Verbin SY Cherbunin RV Auer T Yakovlev DR Bayer M Merkulov IA Stavarache V Reuter D Wieck AD 《Physical review letters》2007,98(10):107401
A key to ultralong electron spin memory in quantum dots (QDs) at zero magnetic field is the polarization of the nuclei, such that the electron spin is stabilized along the average nuclear magnetic field. We demonstrate that spin-polarized electrons in n-doped (In,Ga)As/GaAs QDs align the nuclear field via the hyperfine interaction. A feedback onto the electrons occurs, leading to stabilization of their polarization due to formation of a nuclear spin polaron [I. A. Merkulov, Phys. Solid State 40, 930 (1998)]. Spin depolarization of both systems is consequently greatly reduced, and spin memory of the coupled electron-nuclear spin system is retained over 0.3 sec at temperature of 2 K. 相似文献