217 research outputs found
Resonant control of cold-atom transport through two optical lattices with a constant relative speed
We show theoretically that the dynamics of cold atoms in the lowest energy
band of a stationary optical lattice can be transformed and controlled by a
second, weaker, periodic potential moving at a constant speed along the axis of
the stationary lattice. The atom trajectories exhibit complex behavior, which
depends sensitively on the amplitude and speed of the propagating lattice. When
the speed and amplitude of the moving potential are low, the atoms are dragged
through the static lattice and perform drifting orbits with frequencies an
order of magnitude higher than that corresponding to the moving potential.
Increasing either the speed or amplitude of the moving lattice induces
Bloch-like oscillations within the energy band of the static lattice, which
exhibit complex resonances at critical values of the system parameters. In some
cases, a very small change in these parameters can reverse the atom's direction
of motion. In order to understand these dynamics we present an analytical
model, which describes the key features of the atom transport and also
accurately predicts the positions of the resonant features in the atom's phase
space. The abrupt controllable transitions between dynamical regimes, and the
associated set of resonances, provide a mechanism for transporting atoms
between precise locations in a lattice: as required for using cold atoms to
simulate condensed matter or as a stepping stone to quantum information
processing. The system also provides a direct quantum simulator of acoustic
waves propagating through semiconductor nanostructures in sound analogs of the
optical laser (SASER)
Cluster and group synchronization in delay-coupled networks
We investigate the stability of synchronized states in delay-coupled networks
where synchronization takes place in groups of different local dynamics or in
cluster states in networks with identical local dynamics. Using a master
stability approach, we find that the master stability function shows a discrete
rotational symmetry depending on the number of groups. The coupling matrices
that permit solutions on group or cluster synchronization manifolds show a very
similar symmetry in their eigenvalue spectrum, which helps to simplify the
evaluation of the master stability function. Our theory allows for the
characterization of stability of different patterns of synchronized dynamics in
networks with multiple delay times, multiple coupling functions, but also with
multiple kinds of local dynamics in the networks' nodes. We illustrate our
results by calculating stability in the example of delay-coupled semiconductor
lasers and in a model for neuronal spiking dynamics.Comment: 11 pages, 7 figure
Nonlinear dynamics and band transport in a superlattice driven by a plane wave
A quantum particle transport induced in a spatially-periodic potential by a
propagating plane wave has a number important implications in a range of
topical physical systems. Examples include acoustically driven semiconductor
superlattices and cold atoms in optical crystal. Here we apply kinetic
description of the directed transport in a superlattice beyond standard linear
approximation, and utilize exact path-integral solutions of the semiclassical
transport equation. We show that the particle drift and average velocities have
non-monotonic dependence on the wave amplitude with several prominent extrema.
Such nontrivial kinetic behaviour is related to global bifurcations developing
with an increase of the wave amplitude. They cause dramatic transformations of
the system phase space and lead to changes of the transport regime. We describe
different types of phase trajectories contributing to the directed transport
and analyse their spectral content
Delayed feedback as a means of control of noise-induced motion
Time--delayed feedback is exploited for controlling noise--induced motion in
coherence resonance oscillators. Namely, under the proper choice of time delay,
one can either increase or decrease the regularity of motion. It is shown that
in an excitable system, delayed feedback can stabilize the frequency of
oscillations against variation of noise strength. Also, for fixed noise
intensity, the phenomenon of entrainment of the basic oscillation period by the
delayed feedback occurs. This allows one to steer the timescales of
noise-induced motion by changing the time delay.Comment: 4 pages, 4 figures. In the replacement file Fig. 2 and Fig. 4(b),(d)
were amended. The reason is numerical error found, that affected the
quantitative estimates of correlation time, but did not affect the main
messag
Noise-induced front motion: Signature of a global bifurcation
We show that front motion can be induced by noise in a spatially extended excitable system with a global constraint. Our model system is a semiconductor superlattice exhibiting complex dynamics of electron accumulation and depletion fronts. The presence of noise induces a global change in the dynamics of the system forcing stationary fronts to move through the entire device. We demonstrate the effect of coherence resonance in our model; i.e., there is an optimal level of noise at which the regularity of front motion is enhanced. Physical insight is provided by relating the space-time dynamics of the fronts with a phase-space analysis
Controlling high-frequency collective electron dynamics via single-particle complexity
We demonstrate, through experiment and theory, enhanced high-frequency
current oscillations due to magnetically-induced conduction resonances in
superlattices. Strong increase in the ac power originates from complex
single-electron dynamics, characterized by abrupt resonant transitions between
unbound and localized trajectories, which trigger and shape propagating charge
domains. Our data demonstrate that external fields can tune the collective
behavior of quantum particles by imprinting configurable patterns in the
single-particle classical phase space.Comment: 5 pages, 4 figure
Towards the Heisenberg limit in microwave photon detection by a qubit array
Using an analytically solvable model, we show that a qubit array-based
detector allows to achieve the fundamental Heisenberg limit in detecting single
photons. In case of superconducting qubits, this opens new opportunities for
quantum sensing and communications in the important microwave range.Comment: 6 pages, 3 figure
Filterless Visible-Range Color Sensing and Wavelength-Selective Photodetection Based on Barium/Nickel Codoped Bandgap-Engineered Potassium Sodium Niobate Ferroelectric Ceramics
This work was supported by University of Oulu and the European Research Council (ERC) under the ERC Starting Grant (agreement number 101039110). V.B. acknowledges the EDUFI Fellowship provided by the Finnish National Agency for Education. F.T. and W.C. acknowledge financial support from the European Research Council (ERC) under the
European Union’s Horizon 2020 research and innovation programme (grant agreement no. 101002219). The Institute of Solid State Physics, University of Latvia as the Center of Excellence, has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement no. 739508, project CAMART2.Photosensors, photodetectors, or color sensors are key components for various optical and optoelectronic applications. Semiconductor-based photodetection has been a dominator which is excellent at measuring the photon intensity of incident light. However, the wavelength of the incident light to be measured must be known beforehand and it mostly depends on auxiliary methods to filter unknown wavelengths. Herein, an alternative but simple mechanism that is using a monolithic, bandgap-engineered photoferroelectric ceramic to blindly determine the wavelength and intensity of incident light at the same time is demonstrated. The photoferroelectric compound is Ba- and Ni-codoped (K,Na)NbO3 exhibiting a direct bandgap of ≈2 eV and a spontaneous polarization of ≈0.25 C m−2. The band–band charge carrier transition is confirmed by multiple characterization methods of photoluminescence, photodielectric spectroscopy, and photoconductivity. The existent optoelectrical cumulative effect enabled by the simultaneous narrow bandgap and strong ferroelectricity allows to reliably distinguish the wavelengths of 405, 552, and 660 nm as well as the power density ranging from ≈0.1 to 10 W cm−2, with the photoresponsivity of up to 60 μA W−1. Consequently, this work proposes an alternative to semiconductor-based counterparts for filterless, wavelength-selective photodetection and color sensing. © 2022 The Authors. Solar RRL published by Wiley-VCH GmbH. --//--
Balanov V.A., Temerov F., Pankratov V., Cao W., Bai Y., Filterless Visible-Range Color Sensing and Wavelength-Selective Photodetection Based on Barium/Nickel Codoped Bandgap-Engineered Potassium Sodium Niobate Ferroelectric Ceramics
(2023) Solar RRL, 7 (3), art. no. 2200995, DOI: 10.1002/solr.202200995, https://www.scopus.com/inward/record.uri?eid=2-s2.0-85142936298&doi=10.1002%2fsolr.202200995&partnerID=40&md5=9af5e9b9c683edd409a7a1b15439782e published under theERC Starting Grant (agreement number 101039110); ERC under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 101002219); The Institute of Solid State Physics, University of Latvia as the Center of Excellence, has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement no. 739508, project CAMART2
- …