744 research outputs found
Dawn of Cavity Spintronics
Merging the progress of spintronics with the advancement in cavity quantum
electrodynamics and cavity polaritons, a new field of Cavity Spintronics is
forming, which connects some of the most exciting modern physics, such as
quantum information and quantum optics, with one of the oldest science on the
earth, the magnetism.Comment: 6 pages, 1 figur
Electrical Detection of Magnetization Dynamics via Spin Rectification Effects
The purpose of this article is to review the current status of a frontier in
dynamic spintronics and contemporary magnetism, in which much progress has been
made in the past decade, based on the creation of a variety of micro- and
nano-structured devices that enable electrical detection of magnetization
dynamics. The primary focus is on the physics of spin rectification effects,
which are well suited for studying magnetization dynamics and spin transport in
a variety of magnetic materials and spintronic devices. Intended to be
intelligible to a broad audience, the paper begins with a pedagogical
introduction, comparing the methods of electrical detection of charge and spin
dynamics in semiconductors and magnetic materials respectively. After that it
provides a comprehensive account of the theoretical study of both the angular
dependence and line shape of electrically detected ferromagnetic resonance
(FMR), which is summarized in a handbook formate easy to be used for analyzing
experimental data. We then review and examine the similarity and differences of
various spin rectification effects found in ferromagnetic films, magnetic
bilayers and magnetic tunnel junctions, including a discussion of how to
properly distinguish spin rectification from the spin pumping/inverse spin Hall
effect generated voltage. After this we review the broad applications of
rectification effects for studying spin waves, nonlinear dynamics, domain wall
dynamics, spin current, and microwave imaging. We also discuss spin
rectification in ferromagnetic semiconductors. The paper concludes with both
historical and future perspectives, by summarizing and comparing three
generations of FMR spectroscopy which have been developed for studying
magnetization dynamics.Comment: Review article submitted to Physics Reports. 75 pages, 37 figure
Cavity Spintronics: An Early Review of Recent Progress in the Study of Magnon-Photon Level Repulsion
Light-matter interactions lie at the heart of condensed matter physics,
providing physical insight into material behaviour while enabling the design of
new devices. Perhaps this is most evident in the push to develop quantum
information and spintronic technologies. On the side of quantum information,
engineered light-matter interactions offer a powerful means to access and
control quantum states, while at the same time new insights into spin-photon
manipulation will benefit the development of spintronic technologies. In this
context the recent discovery of hybridization between ferromagnets and cavity
photons has ushered in a new era of light-matter exploration at the crossroads
of quantum information and spintronics. The key player in this rapidly
developing field of cavity spintronics is a quasiparticle, the
cavity-magnon-polariton. In this early review of recent work, the fundamental
behaviour of the cavity-magnon-polariton is summarized and related to the
development of new spintronic applications. In the last few years a
comprehensive theoretical framework of spin-photon hybridization has been
developed. On an intuitive level many features can be described by a model of
coupled oscillators, however the origin of hybridization is only revealed by
considering a comprehensive electrodynamic framework. Here both approaches are
summarized and a quantum description using the input-output formalism is
outlined. Based on this foundation, in depth experimental investigations of the
coupled spin-photon system have been performed. For example, the influence of
hybridization on spin current generation has been revealed and several in-situ
coupling control mechanisms have been developed. The many recent developments
within this field represent only the first steps in what appears to be a bright
future for cavity spintronics.Comment: Preprint version of a book chapter in Solid State Physics Volume 6
Study of the cavity-magnon-polariton transmission line shape
We experimentally and theoretically investigate the microwave transmission
line shape of the cavity-magnon-polariton (CMP) created by inserting a low
damping magnetic insulator into a high quality 3D microwave cavity. While fixed
field measurements are found to have the expected Lorentzian characteristic, at
fixed frequencies the field swept line shape is in general asymmetric. Such
fixed frequency measurements demonstrate that microwave transmission can be
used to access magnetic characteristics of the CMP, such as the field line
width . By developing an effective oscillator model of the microwave
transmission we show that these line shape features are general characteristics
of harmonic coupling. At the same time, at the classical level the underlying
physical mechanism of the CMP is electrodynamic phase correlation and a second
model based on this principle also accurately reproduces the experimental line
shape features. In order to understand the microscopic origin of the effective
coupled oscillator model and to allow for future studies of CMP phenomena to
extend into the quantum regime, we develop a third, microscopic description,
based on a Green's function formalism. Using this method we calculate the
transmission spectra and find good agreement with the experimental results.Comment: 12 pages, 6 figure
Linking Magnon-Cavity Strong Coupling to Magnon-Polaritons through Effective Permeability
Strong coupling in cavity-magnon systems has shown great potential for use in
spintronics and information processing technologies due to the low damping
rates and long coherence times. Although such systems are conceptually similar
to those coupled by magnon-polaritons (MPs), the link between magnon-cavity
coupling and MPs has not been explicitly defined. In this work we establish
such a connection by studying the frequency-wavevector dispersion of a strongly
coupled magnon-cavity system, using a height-adjustable microwave cavity, and
by modelling the observed behaviour through the system's effective
permeability. A polariton gap between the upper and lower coupled modes of the
magnon-cavity system is defined, and is seen to be dependent on the system's
effective filling factor. This gap is equal to the MP polariton gap in the
limit where filling factor = 1, corresponding to the removal of the microwave
cavity. Thus, our work clarifies the connection between magnon-cavity and MP
coupling, improving our understanding of magnon-photon interactions in coupled
systems
Spin dynamical phase and anti-resonance in a strongly coupled magnon-photon system
We experimentally studied a strongly coupled magnon-photon system via
microwave transmission measurements. An anti-resonance, i.e. the suppression of
the microwave transmission, is observed, indicating a relative phase change
between the magnon response and the driving microwave field. We show that this
anti-resonance feature can be used to interpret the phase evolution of the
coupled magnon-microwave system and apply this technique to reveal the phase
evolution of magnon dark modes. Our work provides a standard procedure for the
phase analysis of strongly coupled systems, enabling the phase characterization
of each subsystem, and can be generally applied to other strongly coupled
systems.Comment: 6 pages, 3 figure
Indirect Coupling between Two Cavity Photon Systems via Ferromagnetic Resonance
We experimentally realize indirect coupling between two cavity modes via
strong coupling with the ferromagnetic resonance in Yttrium Iron Garnet (YIG).
We find that some indirectly coupled modes of our system can have a higher
microwave transmission than the individual uncoupled modes. Using a coupled
harmonic oscillator model, the influence of the oscillation phase difference
between the two cavity modes on the nature of the indirect coupling is
revealed. These indirectly coupled microwave modes can be controlled using an
external magnetic field or by tuning the cavity height. This work has potential
for use in controllable optical devices and information processing
technologies
Transient spin current under a thermal switch
In this work, we explore the possibility of enhancing a spin current under a
thermal switch, i.e., connecting the central transport region to two leads in
individual thermal equilibrium abruptly. Using the nonequilibrium Green's
function method for the transient spin current, we obtain a closed-form
solution, which is applicable in the whole nonlinear quantum transport regime
with a significant reduction of computational complexity. Furthermore, we
perform a model calculation on a single-level quantum dot with Lorentzian
linewidth. It shows that the transient spin current may vary spatially, causing
spin accumulation or depletion in the central region. Moreover, general
enhancement of the spin current in the transient regime is observed. In
particular, the in-plane components of the transient spin current may increase
by 2-3 orders of magnitude compared to the steady-state thermoelectric spin
current under a temperature difference of 30 K. Our research demonstrates that
ultrafast enhancement of spin currents can be effectively achieved by thermal
switches.Comment: Submitted to J. Phys. D: Appl. Phys.
(http://iopscience.iop.org/article/10.1088/1361-6463/aac7ca/meta
Ultrafast Manipulation of a Double Quantum Dot via Lyapunov Control Method
For a double quantum dot (DQD) system, here we propose alternative ultrafast
manipulate approach: Lyapunov control method, to transfer the state from R to L
on the picosecond scale, orders of magnitude faster and transfer probability
higher than the previously measured electrically controlled charge- or
spin-based quits. The control laws are composed of two-direction components,
one is used to eliminate the dissipation in the system, another is used to
transfer the state. The control theory's stability ensures the system can be
transferred to the target state in high probability, and the coefficients in
control laws leads very fast convergence. The role of eliminating the
dissipation plays the suppression of decoherence effect. Numerical simulation
results show that under the realistic implementation conditions, the transfer
probability and fidelity can be increased up to 98.79% and 98.97%,
respectively. This is the first result directly applicable to a DQD system's
state transferring using the Lyapunov control method. We also give specific
experimental realization scheme.Comment: 8 pages, 4 figure
Cavity mediated manipulation of distant spin currents using cavity-magnon-polariton
Using electrical detection of a strongly coupled spin-photon system comprised
of a microwave cavity mode and two magnetic samples, we demonstrate the long
distance manipulation of spin currents. This distant control is not limited by
the spin diffusion length, instead depending on the interplay between the local
and global properties of the coupled system, enabling systematic spin current
control over large distance scales (several centimeters in this work). This
flexibility opens the door to improved spin current generation and manipulation
for cavity spintronic devices.Comment: 5 pages, 3 figure
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