176 research outputs found
Microwave-induced resistance oscillations and zero-resistance states in 2D electron systems with two occupied subbands
We report on theoretical studies of recently discovered microwave-induced
resistance oscillations and zero resistance states in Hall bars with two
occupied subbands. In the same results, resistance presents a peculiar shape
which appears to have a built-in interference effect not observed before. We
apply the microwave-driven electron orbit model, which implies a
radiation-driven oscillation of the two-dimensional electron system. Thus, we
calculate different intra and inter-subband electron scattering rates and times
that are revealing as different microwave-driven oscillations frequencies for
the two electronic subbands. Through scattering, these subband-dependent
oscillation motions interfere giving rise to a striking resistance profile. We
also study the dependence of irradiated magnetoresistance with power and
temperature. Calculated results are in good agreement with experiments.Comment: 7 pages, 6 figure
Polarization immunity of magnetoresistivity response under Microwave excitation
We analyze theoretically the dependence of the microwave polarization sate
and sense on the magnetoresistivity response of two-dimensional electron
systems. Linear and circular polarization have been considered with different
senses and directions. We discuss the polarization dependence of the
longitudinal magnetoresistivity and propose an explanation for the
experimentally observed polarization immunity, i.e., resistivity oscillations
and zero resistance state regions are unaffected by the sense of circular
polarization or by the direction of microwave electric field.Comment: 4 pages and 1 figur
Optimizing edge state transfer in a Su-Schrieffer-Heeger chain via hybrid digital-analog strategies
Su-Schrieffer-Heeger (SSH) chain, serving as a paradigmatic model for
comprehending topological phases and their associated edge states, plays a
pivotal role in advancing our understanding of quantum materials and quantum
information processing and technology. In this paper, we introduce a hybrid
analog-digital protocol designed for the non-adiabatic yet high-fidelity
transfer of edge states in a SSH chain, featuring two sublattices A and B. The
core of our approach lies in harnessing the approximate time-dependent
counter-diabatic (CD) interaction, derived from adiabatic gauge potentials.
However, to enhance transfer fidelity, particularly in long-distance chains,
higher-order nested commutators become crucial. To simplify experimental
implementation and navigate computational complexities, we identify the
next-to-nearest-neighbour (NNN) hopping terms between sublattice A as dominant
CD drivings, and further optimize them by using variational quantum circuits.
Through digital quantum simulation, our protocol showcases the capability to
achieve rapid and robust solutions, even in the presence of disorder. This
analog-digital transfer protocol, an extension of quantum control methodology,
establishes a robust framework for edge state transfer. Importantly, the
optimal CD drivings identified can be seamlessly implemented across various
quantum registers, highlighting the versatility of our approach
Photon-resolved Floquet theory in open quantum systems
Photon-resolved Floquet theory keeps track of the photon exchange of a
quantum system with a coherent driving field. It thus complements the standard
full-counting statistics that counts the number of photons exchanged with
incoherent photon modes giving rise to dissipation. In this paper, we introduce
a unifying framework describing both situations. We develop methods suitable
for an analytical evaluation of low-order cumulants of photonic probability
distributions. Within this framework we analyze the two-mode Jaynes-Cummings
model to demonstrate that the Photon-resolved Floquet theory and the standard
full-counting statistics make consistent statistical predictions.
Interestingly, we find that the photon-flux fluctuations diverge for vanishing
dissipation, which can be related to an entanglement effect between the driven
matter system and the driving field. To substantiate our results, we use our
framework to describe efficient photon up-conversion in an ac-driven lambda
system, that is characterized by a high signal-to-noise ratio. As the framework
is non-perturbative and predicts fluctuations, it paves the way towards
non-perturbative spectroscopy, which will assist to improve metrological
methods.Comment: 25 pages, 6 figures, 4 appendices. Comments are welcom
Effect of a in-plane magnetic field on the microwave assisted magnetotransport in a two-dimensional electron system
In this work we present a theoretical approach to study the effect of an
in-plane (parallel) magnetic field on the microwave-assisted transport
properties of a two-dimensional electron system. Previous experimental
evidences show that microwave-induced resistance oscillations and zero
resistance states are differently affected depending on the experimental
set-up: two magnetic fields (two-axis magnet) or one tilted magnetic field. In
the first case, experiments report a clear quenching of resistance oscillations
and zero resistance states. In a tilted field, one obtains oscillations
displacement and quenching but the latter is unbalanced and less intense. In
our theoretical proposal we explain these results in terms of the
microwave-driven harmonic motion performed by the electronic orbits and how
this motion is increasingly damped by the in-plane field.Comment: Figure 1 has been change
Canted phase in double quantum dots
We perform a Hartree-Fock calculation in order to describe the ground state
of a vertical double quantum dot in the absence of magnetic fields parallel to
the growth direction. Intra- and interdot exchange interactions determine the
singlet or triplet character of the system as the tunneling is tuned. At finite
Zeeman splittings due to in-plane magnetic fields, we observe the continuous
quantum phase transition from ferromagnetic to symmetric phase through a canted
antiferromagnetic state. The latter is obtained even at zero Zeeman energy for
an odd electron number.Comment: 5 pages, 3 figure
Coherent and sequential photoassisted tunneling through a semiconductor double barrier structure
We have studied the problem of coherent and sequential tunneling through a
double barrier structure, assisted by light considered to be present All over
the structure, i,e emitter, well and collector as in the experimental evidence.
By means of a canonical transformation and in the framework of the time
dependent perturbation theory, we have calculated the transmission coefficient
and the electronic resonant current. Our calculations have been compared with
experimental results turning out to be in good agreement. Also the effect on
the coherent tunneling of a magnetic field parallel to the current in the
presence of light, has been considered.Comment: Revtex3.0, 8figures uuencoded compressed tar-fil
Classical wave experiments on chaotic scattering
We review recent research on the transport properties of classical waves
through chaotic systems with special emphasis on microwaves and sound waves.
Inasmuch as these experiments use antennas or transducers to couple waves into
or out of the systems, scattering theory has to be applied for a quantitative
interpretation of the measurements. Most experiments concentrate on tests of
predictions from random matrix theory and the random plane wave approximation.
In all studied examples a quantitative agreement between experiment and theory
is achieved. To this end it is necessary, however, to take absorption and
imperfect coupling into account, concepts that were ignored in most previous
theoretical investigations. Classical phase space signatures of scattering are
being examined in a small number of experiments.Comment: 33 pages, 13 figures; invited review for the Special Issue of J.
Phys. A: Math. Gen. on "Trends in Quantum Chaotic Scattering
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