6,175 research outputs found
Determination of spin polarization in InAs/GaAs self-assembled quantum dots
The spin polarization of electrons trapped in InAs self-assembled quantum dot
ensembles is investigated. A statistical approach for the population of the
spin levels allows one to infer the spin polarization from the measure values
of the addition energies. From the magneto-capacitance spectroscopy data, the
authors found a fully polarized ensemble of electronic spins above 10 T when
and at 2.8 K. Finally, by including the g-tensor
anisotropy the angular dependence of spin polarization with the magnetic field
orientation and strength could be determined.Comment: 3 pages, 2 figures, Accepted Appl. Phys. Let
Rehybridization of electronic structure in compressed two-dimensional quantum dot superlattices
Two-dimensional superlattices of organically passivated 2.6-nm silver quantum dots were prepared as Langmuir monolayers and transferred to highly oriented pyrolytic graphite substrates. The structural and electronic properties of the films were probed with variable temperature scanning tunneling microscopy. Particles passivated with decanethiol (interparticle separation distance of ∼1.1±0.2 nm) exhibited Coulomb blockade and staircase. For particles passivated with hexanethiol or pentanethiol (interparticle separation distance of ∼0.5±0.2 nm), the single-electron charging was quenched, and the redistribution of the density of states revealed that strong quantum mechanical exchange, i.e., wave-function hybridization, existed among the particles in these films
Causal Structure and Birefringence in Nonlinear Electrodynamics
We investigate the causal structure of general nonlinear electrodynamics and
determine which Lagrangians generate an effective metric conformal to
Minkowski. We also proof that there is only one analytic nonlinear
electrodynamics presenting no birefringence.Comment: 11 pages, no figure
Geometrical CP violation in multi-Higgs models
We introduce several methods to obtain calculable phases with geometrical
values that are independent of arbitrary parameters in the scalar potential.
These phases depend on the number of scalars and on the order of the discrete
non-Abelian group considered. Using these methods we present new geometrical CP
violation candidates with vacuum expectation values that must violate CP (the
transformation that would make them CP conserving is not a symmetry of the
potential). We also extend to non-renormalisable potentials the proof that more
than two scalars are needed to obtain these geometrical CP violation
candidates.Comment: 8 pages, 2 figures. v2: table added, accepted by JHE
Lande g-tensor in semiconductor nanostructures
Understanding the electronic structure of semiconductor nanostructures is not
complete without a detailed description of their corresponding spin-related
properties. Here we explore the response of the shell structure of InAs
self-assembled quantum dots to magnetic fields oriented in several directions,
allowing the mapping of the g-tensor modulus for the s and p shells. We found
that the g-tensors for the s and p shells show a very different behavior. The
s-state in being more localized allows the probing of the confining potential
details by sweeping the magnetic field orientation from the growth direction
towards the in-plane direction. As for the p-state, we found that the g-tensor
modulus is closer to that of the surrounding GaAs, consistent with a larger
delocalization. These results reveal further details of the confining
potentials of self-assembled quantum dots that have not yet been probed, in
addition to the assessment of the g-tensor, which is of fundamental importance
for the implementation of spin related applications.Comment: 4 pages, 4 figure
Microstrip resonator for microwaves with controllable polarization
In this work the authors implemented a resonator based upon microstrip
cavities that permits the generation of microwaves with arbitrary polarization.
Design, simulation, and implementation of the resonators were performed using
standard printed circuit boards. The electric field distribution was mapped
using a scanning probe cavity perturbation technique. Electron spin resonance
using a standard marker was carried out in order to verify the polarization
control from linear to circular.Comment: 3 pages, 3 figures, submitted to Appl. Phys. Let
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Optimizing survival outcomes with post-remission therapy in acute myeloid leukemia.
Optimization of post-remission therapies to maintain complete remission and prevent relapse is a major challenge in treating patients with acute myeloid leukemia (AML). Monitoring patients for measurable residual disease (MRD) is helpful to identify those at risk for relapse. Hypomethylating agents are being investigated as post-remission therapy. Identification of recurrent genetic alterations that drive disease progression has enabled the design of new, personalized approaches to therapy for patients with AML. Emerging data suggest that targeted post-remission therapy, alone or in combination with chemotherapy, may improve outcomes. Results of ongoing clinical trials will further define potential clinical benefits
Condensation of Vortex-Strings: Effective Potential Contribution Through Dual Actions
Topological excitations are believed to play an important role in different
areas of physics. For example, one case of topical interest is the use of dual
models of quantum cromodynamics to understand properties of its vacuum and
confinement through the condensation of magnetic monopoles and vortices. Other
applications are related to the role of these topological excitations,
nonhomogeneous solutions of the field equations, in phase transitions
associated to spontaneous symmetry breaking in gauge theories, whose study is
of importance in phase transitions in the early universe, for instance. Here we
show a derivation of a model dual to the scalar Abelian Higgs model where its
topological excitations, namely vortex-strings, become manifest and can be
treated in a quantum field theory way. The derivation of the nontrivial
contribution of these vacuum excitations to phase transitions and its analogy
with superconductivity is then made possible and they are studied here.Comment: 7 pages. Based on a talk given by R. O. Ramos at the Infrared QCD in
Rio conference, Rio de Janeiro, Brazil, June 5-9, 200
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