38 research outputs found
A matrix solution to pentagon equation with anticommuting variables
We construct a solution to pentagon equation with anticommuting variables
living on two-dimensional faces of tetrahedra. In this solution, matrix
coordinates are ascribed to tetrahedron vertices. As matrix multiplication is
noncommutative, this provides a "more quantum" topological field theory than in
our previous works
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 -doped quantum well structures corresponds to recent
experimental observations.Comment: 5 pages, 2 figures, to be published in JETP Letter
Experimental Separation of Rashba and Dresselhaus Spin-Splittings in Semiconductor Quantum Wells
The relative strengths of Rashba and Dresselhaus terms describing the
spin-orbit coupling in semiconductor quantum well (QW) structures are extracted
from photocurrent measurements on n-type InAs QWs containing a two-dimensional
electron gas (2DEG). This novel technique makes use of the angular distribution
of the spin-galvanic effect at certain directions of spin orientation in the
plane of a QW. The ratio of the relevant Rashba and Dresselhaus coefficients
can be deduced directly from experiment and does not relay on theoretically
obtained quantities. Thus our experiments open a new way to determine the
different contributions to spin-orbit coupling
Symmetry and spin dephasing in (110)-grown quantum wells
Symmetry and spin dephasing of in (110)-grown GaAs quantum wells (QWs) are
investigated applying magnetic field induced photogalvanic effect (MPGE) and
time-resolved Kerr rotation. We show that MPGE provides a tool to probe the
symmetry of (110)-grown quantum wells. The photocurrent is only observed for
asymmetric structures but vanishes for symmetric QWs. Applying Kerr rotation we
prove that in the latter case the spin relaxation time is maximal, therefore
these structures set upper limit of spin dephasing in GaAs QWs. We also
demonstrate that structure inversion asymmetry can be controllably tuned to
zero by variation of delta-doping layer position.Comment: 4 pages, 4 figure
Spin-dependent tunnelling through a symmetric barrier
The problem of electron tunnelling through a symmetric semiconductor barrier
based on zinc-blende-structure material is studied. The Dresselhaus terms
in the effective Hamiltonian of bulk semiconductor of the barrier are shown to
result in a dependence of the tunnelling transmission on the spin orientation.
The difference of the transmission probabilities for opposite spin orientations
can achieve several percents for the reasonable width of the barriers.Comment: 3 pages, Submitted to Phys. Rev.
On the Role of FSI in K -> 2\pi Decay
Contrary to wide-spread opinion that the final state interaction (FSI)
enlarges the amplitude , we argue that FSI is not able to
increase the absolute value of this amplitude.Comment: 10 pages, minor correction