21 research outputs found
Interplay between Zeeman interaction and spin-orbit coupling in a two-dimensional semiconductor system
We analyse the interplay between Dresselhaus, Bychkov-Rashba, and Zeeman
interactions in a two-dimensional semiconductor quantum system under the action
of a magnetic field. When a vertical magnetic field is considered, we predict
that the interplay results in an effective cyclotron frequency that depends on
a spin-dependent contribution. For in-plane magnetic fields, we found that the
interplay induces an anisotropic effective gyromagnetic factor that depends on
the orientation of the applied field as well as on the orientation of the
electron momentum.Comment: 5 page
Renormalization of spin-orbit coupling in quantum dots due to Zeeman interaction
We derive analitycally a partial diagonalization of the Hamiltonian
representing a quantum dot including spin-orbit interaction and Zeeman energy
on an equal footing. It is shown that the interplay between these two terms
results in a renormalization of the spin-orbit intensity. The relation between
this feature and experimental observations on conductance fluctuations is
discussed, finding a good agreement between the model predictions and the
experimental behavior.Comment: 4 pages, no figures. To appear in Phys. Rev. B (Brief Report) (2004
Intrinsic spin dynamics in semiconductor quantum dots
We investigate the characteristic spin dynamics corresponding to
semiconductor quantum dots within the multiband envelope function approximation
(EFA). By numerically solving an Hamiltonian we treat
systems based on different III-V semiconductor materials.It is shown that, even
in the absence of an applied magnetic field, these systems show intrinsic spin
dynamics governed by intraband and interband transitions leading to
characteristic spin frequencies ranging from the THz to optical frequencies.Comment: to be published in Nanotechnology. Separated figure file
Electronic spin precession in semiconductor quantum dots with spin-orbit coupling
The electronic spin precession in semiconductor dots is strongly affected by
the spin-orbit coupling. We present a theory of the electronic spin resonance
at low magnetic fields that predicts a strong dependence on the dot occupation,
the magnetic field and the spin-orbit coupling strength. Coulomb interaction
effects are also taken into account in a numerical approach.Comment: 5 pages, 4 figure
Predicted signatures of the intrinsic spin Hall effect in closed systems
We study a two-dimensional electron system in the presence of spin-orbit
interaction. It is shown analytically that the spin-orbit interaction acts as a
transversal effective electric field, whose orientation depends on the sign of
the -axis spin projection. This effect doesn't require any driving
external field and is inherent to the spin-orbit interactions present in
semiconductor materials. Therefore, it should manifest in both closed and open
systems. It is proposed an experiment to observe the intrinsic spin Hall effect
in the far infrared absorption of an asymmetric semiconductor nanostructure.Comment: accepted for publication in Physical Review Letter
Spin control in semiconductor quantum wires
We show that spin-flip rotation in a semiconductor quantum wire, caused by
the Rashba and the Dresselhaus interactions (both of arbitrary strengths), can
be suppressed by dint of an in-plane magnetic field. We found a new type of
symmetry, which arises at a particular set of intensity and orientation of the
magnetic field and explains this suppression. Based on our findings, we propose
a transport experiment to measure the strengths of the Rashba and the
Dresselhaus interactions.Comment: 4 pages, 4 figure
Anisotropic universal conductance fluctuations in disordered quantum wires with Rashba and Dresselhaus spin-orbit interaction and applied in-plane magnetic field
We investigate the transport properties of narrow quantum wires realized in
disordered two-dimensional electron gases in the presence of k-linear Rashba
and Dresselhaus spin-orbit interaction (SOI), and an applied in-plane magnetic
field. Building on previous work [Scheid, et al., PRL 101, 266401 (2008)], we
find that in addition to the conductance, the universal conductance
fluctuations also feature anisotropy with respect to the magnetic field
direction. This anisotropy can be explained solely from the symmetries
exhibited by the Hamiltonian as well as the relative strengths of the Rashba
and Dresselhaus spin orbit interaction and thus can be utilized to detect this
ratio from purely electrical measurements.Comment: 10 pages, 4 figures, 1 tabl
Deteção remota aplicada à rega dos espaços verdes urbanos
A nova cultura da água visa a conservação dos recursos naturais e o aumento do rendimento
produtivo da água nos espaços verdes públicos e privados. Estes espaços assumem uma
relevância no bem-estar e na qualidade de vida das populações urbanas. No entanto, o aumento
da área verde em climas mediterrâneos estará inevitavelmente associado ao aumento do
consumo em água. A rega surge com a finalidade de fazer face Ă s necessidades hĂdricas das
plantas em função das caraterĂsticas climáticas da regiĂŁo. Esta situação Ă© mais relevante quando a
escolha das plantas não recai sobre as autóctones e a água para a rega tem origem na rede de
distribuição de água potável. Nos Ăşltimos anos, alguns municĂpios em Portugal tĂŞm vindo a
implementar a instalação de dois tipos distintos de contadores de água: consumo doméstico e
rega. Assim, garante-se água para rega com tarifário de menor custo, visto não incluir tratamento
de água residual. Desde 2012, que a vila de São Brás de Alportel implementou este sistema de
rega para os jardins privados. O presente trabalho tem como objetivos o estudo da evolução dos
consumos de água na rega dos espaços verdes privados que aderiram a este sistema e a monitorização da rega nos espaços verdes públicos, para uma gestão sustentável da água. A
monitorização será realizada pela avaliação da qualidade dos espaços verdes através da deteção
remota, integrada com a informação dos dados climáticos e dos consumos de água.info:eu-repo/semantics/publishedVersio
Rectangular quantum dots in high magnetic fields
We use density-functional methods to study the effects of an external
magnetic field on two-dimensional quantum dots with a rectangular hard-wall
confining potential. The increasing magnetic field leads to spin polarization
and formation of a highly inhomogeneous maximum-density droplet at the
predicted magnetic field strength. At higher fields, we find an oscillating
behavior in the electron density and in the magnetization of the dot. We
identify a rich variety of phenomena behind the periodicity and analyze the
complicated many-electron dynamics, which is shown to be highly dependent on
the shape of the quantum dot.Comment: 6 pages, 6 figures, submitted to Phys. Rev.
Dynamical spin-electric coupling in a quantum dot
Due to the spin-orbital coupling in a semiconductor quantum dot, a freely
precessing electron spin produces a time-dependent charge density. This creates
a sizeable electric field outside the dot, leading to promising applications in
spintronics. The spin-electric coupling can be employed for non-invasive single
spin detection by electrical methods. We also consider a spin relaxation
mechanism due to long-range coupling to electrons in gates and elsewhere in the
system, and find a contribution comparable to, and in some cases dominant over
previously discussed mechanisms.Comment: 4 pages, 2 figure