74,899 research outputs found
Delay time and tunneling transient phenomena
Analytic solutions to the time-dependent Schr\"odinger equation for cutoff
wave initial conditions are used to investigate the time evolution of the
transmitted probability density for tunneling. For a broad range of values of
the potential barrier opacity , we find that the probability density
exhibits two evolving structures. One refers to the propagation of a {\it
forerunner} related to a {\it time domain resonance} [Phys. Rev. A {\bf 64},
0121907 (2001)], while the other consists of a semiclassical propagating
wavefront. We find a regime where the {\it forerunners} are absent,
corresponding to positive {\it time delays}, and show that this regime is
characterized by opacities . The critical opacity
is derived from the analytical expression for the {\it delay time}, that
reflects a link between transient effects in tunneling and the {\it delay time}Comment: To be published in Physical Review
Delay Time in Quaternionic Quantum Mechanics
In looking for quaternionic violations of quantum mechanics, we discuss the
delay time for pure quaternionic potentials. The study shows in which energy
region it is possible to amplify the difference between quaternionic and
complex quantum mechanics.Comment: 9 pages, 5 figure
Delay time computation for relativistic tunneling particles
We study the tunneling zone solutions of a one-dimensional electrostatic
potential for the relativistic (Dirac to Klein-Gordon) wave equation when the
incoming wave packet exhibits the possibility of being almost totally
transmitted through the barrier. The transmission probabilities, the phase
times and the dwell times for the proposed relativistic dynamics are obtained
and the conditions for the occurrence of accelerated tunneling transmission are
all quantified. We show that, in some limiting cases, the analytical
difficulties that arise when the stationary phase method is employed for
obtaining phase (traversal) tunneling times are all overcome. Lessons
concerning the phenomenology of the relativistic tunneling suggest revealing
insights into condensed-matter experiments using electrostatic barriers for
which the accelerated tunneling effect can be observed.Comment: 17 pages, 4 figure
Characteristics of a Delayed System with Time-dependent Delay Time
The characteristics of a time-delayed system with time-dependent delay time
is investigated. We demonstrate the nonlinearity characteristics of the
time-delayed system are significantly changed depending on the properties of
time-dependent delay time and especially that the reconstructed phase
trajectory of the system is not collapsed into simple manifold, differently
from the delayed system with fixed delay time. We discuss the possibility of a
phase space reconstruction and its applications.Comment: 4 pages, 6 figures (to be published in Phys. Rev. E
Phase delay time and superluminal propagation in barrier tunneling
In this work we study the behaviour of Wigner phase delay time for tunneling
in the reflection mode. Our system consists of a circular loop connected to a
single wire of semi-infinite length in the presence of Aharonov-Bohm flux. We
calculate the analytical expression for the saturated delay time. This
saturated delay time is independent of Aharonov- Bohm flux and the width of the
opaque barrier thereby generalizing the Hartman effect. This effect implies
superluminal group velocities as a consequence. We also briefly discuss the
concept called "space collapse or space destroyer".Comment: 5 pages, 5 figure
Distribution of Wigner delay time from single channel disordered systems
We consider the scattering of an electron from a semi-infinite
one-dimensional random medium. The random medium is characterized by force,
-\d V/\d L being the basic random variable. We obtain an analytical
expression for the stationary delay time () distribution
within a random phase approximation. Our result agrees with earlier analytical
expressions, where the random potential is taken to be of different kind,
indicating universality of the delay time distribution, i.e., delay time
distribution is independent of the nature of disorder.Comment: 8 pages RevTeX, no figure
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