1,922 research outputs found
Ratchet effects in two-dimensional systems with a lateral periodic potential
Radiation-induced ratchet electric currents have been studied theoretically
in graphene with a periodic noncentrosymmetric lateral potential. The ratchet
current generated under normal incidence is shown to consist of two
contributions, one of them being polarization-independent and proportional to
the energy relaxation time, and another controlled solely by elastic scattering
processes and sensitive to both the linear and circular polarization of
radiation. Two realistic mechanisms of electron scattering in graphene are
considered. For short-range defects, the ratchet current is helicity-dependent
but independent of the direction of linear polarization. For the Coulomb
impurity scattering, the ratchet current is forbidden for the radiation
linearly polarized in the plane perpendicular to the lateral-potential
modulation direction. For comparison, the ratchet currents in a quantum well
with a lateral superlattice are calculated at low temperatures with allowance
for the dependence of the momentum relaxation time on the electron energy.Comment: 8 pages, 4 figure
Electric field control of spin-orbit splittings in GaAs/AlGaAs coupled quantum wells
Electron spin dynamics is investigated in n-i-n GaAs/AlGaAs coupled quantum
wells. The electron spin dephasing time is measured as a function of an
external electrical bias under resonant excitation of the 1sHH intrawell
exciton using a time-resolved Kerr rotation technique. It is found a strong
electron spin dephasing time anisotropy caused by an interference of the
structure inversion asymmetry and the bulk inversion asymmetry. This anisotropy
is shown to be controlled by an electrical bias. A theoretical analysis of
electron spin dephasing time anisotropy is developed. The ratio of Rashba and
Dresselhaus spin splittings is studied as a function of applied bias.Comment: 4 pages, 3 figure
Tuning of structure inversion asymmetry by the -doping position in (001)-grown GaAs quantum wells
Structure and bulk inversion asymmetry in doped (001)-grown GaAs quantum
wells is investigated by applying the magnetic field induced photogalvanic
effect. We demonstrate that the structure inversion asymmetry (SIA) can be
tailored by variation of the delta-doping layer position. Symmetrically-doped
structures exhibit a substantial SIA due to impurity segregation during the
growth process. Tuning the SIA by the delta-doping position we grow samples
with almost equal degrees of structure and bulk inversion asymmetry.Comment: 4 pages 2 figure
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