3,292 research outputs found
A mesoscopic Tera-hertz pulse detector
We show that, under the passage of an electromagnetic terahertz pulse, an
asymmetric double barrier device may act as an on/off current switch, depending
on the bias. The time-dependent response of the device is discussed.Comment: 3 pages Revtex, 4 PS figures. To appear in Applied Physics Letter
Dicke effect in a quantum wire with side-coupled quantum dots
A system of an array of side-coupled quantum-dots attached to a quantum wire
is studied theoretically. Transport through the quantum wire is investigated by
means of a noninteracting Anderson tunneling Hamiltonian. Analytical
expressions of the transmission probability and phase are given. The
transmission probability shows an energy spectrum with forbidden and allowed
bands that depends on the up-down asymmetry of the system. In up-down symmetry
only the gap survives, and in up-down asymmetry an allowed band is formed. We
show that the allowed band arises by the indirect coupling between the up and
down quantum dots. In addition, the band edges can be controlled by the degree
of asymmetry of the quantum dots. We discuss the analogy between this
phenomenon with the Dicke effect in optics.Comment: 11 pages, 5 figures. To appear in Physica
Monetary policy rules in a small open economy: An application to Mexico
We estimate a small-scale macro model for the Mexican economy under the New Keynesian (NK) framework and alternative interest rate rules for Mexico. With these results we evaluate the performance of the Bank of Mexico against a set of optimality principles derived in the NK literature. We show that the Bank of Mexico holds a preference for stabilizing not only inflation around target, but also acts to achieve an output gap close to zero. Furthermore, we show the central bank responds non-linearly to real exchange rate depreciations. We also show that, although the central bank has attempted to contain inflation, it has not conclusively satisfied the Taylor principle, so moderate inflation during the period may be partly a consequence of a favorable macroeconomic environment, rather than active policy.Taylor Rule, New Keynesian, Monetary Policy, Interest Rate Rules, Small Open Economy
Bound states in the continuum driven by AC fields
We report the formation of bound states in the continuum driven by AC fields.
This system consists of a quantum ring connected to two leads. An AC side-gate
voltage controls the interference pattern of the electrons passing through the
system. We model the system by two sites in parallel connected to two
semi-infinite lattices. The energy of these sites change harmonically with
time. We obtain the transmission probability and the local density of states at
the ring sites as a function of the parameters that define the system. The
transmission probability displays a Fano profile when the energy of the
incoming electron matches the driving frequency. Correspondingly, the local
density of states presents a narrow peak that approaches a Dirac delta function
in the weak coupling limit. We attribute these features to the presence of
bound states in the continuum.Comment: 5 pages, 3 figure
Dynamic instability in resonant tunneling
We show that an instability may be present in resonant tunneling through a
quantum well in one, two and three dimensions, when the resonance lies near the
emitter Fermi level. A simple semiclassical model which simulates the resonance
and the projected density of states by a nonlinear conductor, the Coulomb
barrier by a capacitance, and the time evolution by an iterated map, is used.
The model reproduces the observed hysteresis in such devices, and exhibits a
series of bifurcations leading to fast chaotic current fluctuations.Comment: 7 pages, 2 figure
Transport in random quantum dot superlattices
We present a novel model to calculate single-electron states in random
quantum dot superlattices made of wide-gap semiconductors. The source of
disorder comes from the random arrangement of the quantum dots (configurational
disorder) as well as spatial inhomogeneities of their shape (morphological
disorder). Both types of disorder break translational symmetry and prevent the
formation of minibands, as occurs in regimented arrays of quantum dots. The
model correctly describes channel mixing and broadening of allowed energy bands
due to elastic scattering by disorder
Non-Linear Effects in Resonant Tunneling; Bistabilities and Self-Sustained Oscillating Currents
We study non-linear phenomena in double barrier heterostructures. Systems in
3D under the effect of an external magnetic field along the current and 1D
systems are analyzed. Non-linearities are reflected in the I-V characteristic
curve as bistabilities, instabilities and time dependent oscillations of the
currents. The nature of the non-linear behavior depends upon the parameters
that define the system.Comment: 3 pages, 2 figures, accepted for publication in Superlattices and
Microstructure
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