16,110 research outputs found
Temperature effect on (2+1) experimental Kardar-Parisi-Zhang growth
We report on the effect of substrate temperature (T) on both local structure
and long-wavelength fluctuations of polycrystalline CdTe thin films deposited
on Si(001). A strong T-dependent mound evolution is observed and explained in
terms of the energy barrier to inter-grain diffusion at grain boundaries, as
corroborated by Monte Carlo simulations. This leads to transitions from
uncorrelated growth to a crossover from random-to-correlated growth and
transient anomalous scaling as T increases. Due to these finite-time effects,
we were not able to determine the universality class of the system through the
critical exponents. Nevertheless, we demonstrate that this can be circumvented
by analyzing height, roughness and maximal height distributions, which allow us
to prove that CdTe grows asymptotically according to the Kardar-Parisi-Zhang
(KPZ) equation in a broad range of T. More important, one finds positive
(negative) velocity excess in the growth at low (high) T, indicating that it is
possible to control the KPZ non-linearity by adjusting the temperature.Comment: 6 pages, 5 figure
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
Dynamics of a single exciton in strongly correlated bilayers
We formulated an effective theory for a single interlayer exciton in a
bilayer quantum antiferromagnet, in the limit that the holon and doublon are
strongly bound onto one interlayer rung by the Coulomb force. Upon using a rung
linear spin wave approximation of the bilayer Heisenberg model, we calculated
the spectral function of the exciton for a wide range of the interlayer
Heisenberg coupling \alpha=J_{\perp}/Jz. In the disordered phase at large
\alpha, a coherent quasiparticle peak appears representing free motion of the
exciton in a spin singlet background. In the N\'{e}el phase, which applies to
more realistic model parameters, a ladder spectrum arises due to Ising
confinement of the exciton. The exciton spectrum is visible in measurements of
the dielectric function, such as c-axis optical conductivity measurements.Comment: 28 pages, 12 figure
Magnetocaloric effect in integrable spin-s chains
We study the magnetocaloric effect for the integrable antiferromagnetic
high-spin chain. We present an exact computation of the Gr\"uneisen parameter,
which is closely related to the magnetocaloric effect, for the quantum spin-s
chain on the thermodynamical limit by means of Bethe ansatz techniques and the
quantum transfer matrix approach. We have also calculated the entropy S and the
isentropes in the (H,T) plane. We have been able to identify the quantum
critical points H_c^{(s)}=2/(s+1/2) looking at the isentropes and/or the
characteristic behaviour of the Gr\"uneisen parameter.Comment: 6 pages, 3 figure
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