108,297 research outputs found
Radiation induced oscillations of the Hall resistivity in two-dimensional electron systems
We consider the effect of microwave radiation on the Hall resistivity in
two-dimension electron systems. It is shown that the photon-assisted impurity
scattering of electrons can result in oscillatory dependences of both
dissipative and Hall components of the conductivity and resistivity tensors on
the ratio of radiation frequency to cyclotron frequency. The Hall resistivity
can include a component induced by microwave radiation which is an even
function of the magnetic field. The phase of the dissipative resistivity
oscillations and the polarization dependence of their amplitude are compared
with those of the Hall resistivity oscillations. The developed model can
clarify the results of recent experimental observations of the radiation
induced Hall effect.Comment: 4 pages, 1 figur
Radiation induced oscillatory Hall effect in high mobility GaAs/AlGaAs devices
We examine the radiation induced modification of the Hall effect in high
mobility GaAs/AlGaAs devices that exhibit vanishing resistance under microwave
excitation. The modification in the Hall effect upon irradiation is
characterized by (a) a small reduction in the slope of the Hall resistance
curve with respect to the dark value, (b) a periodic reduction in the magnitude
of the Hall resistance, , that correlates with an increase in the
diagonal resistance, , and (c) a Hall resistance correction that
disappears as the diagonal resistance vanishes.Comment: 4 pages text, 4 color figure
Hall Effect Gyrators and Circulators
The electronic circulator, and its close relative the gyrator, are invaluable
tools for noise management and signal routing in the current generation of
low-temperature microwave systems for the implementation of new quantum
technologies. The current implementation of these devices using the Faraday
effect is satisfactory, but requires a bulky structure whose physical dimension
is close to the microwave wavelength employed. The Hall effect is an
alternative non-reciprocal effect that can also be used to produce desired
device functionality. We review earlier efforts to use an ohmically-contacted
four-terminal Hall bar, explaining why this approach leads to unacceptably high
device loss. We find that capacitive coupling to such a Hall conductor has much
greater promise for achieving good circulator and gyrator functionality. We
formulate a classical Ohm-Hall analysis for calculating the properties of such
a device, and show how this classical theory simplifies remarkably in the
limiting case of the Hall angle approaching 90 degrees. In this limit we find
that either a four-terminal or a three-terminal capacitive device can give
excellent circulator behavior, with device dimensions far smaller than the a.c.
wavelength. An experiment is proposed to achieve GHz-band gyration in
millimetre (and smaller) scale structures employing either semiconductor
heterostructure or graphene Hall conductors. An inductively coupled scheme for
realising a Hall gyrator is also analysed.Comment: 18 pages, 15 figures, ~5 MB. V3: sections V-VIII revisited plus other
minor changes, Fig 2 added. Submitted to PR
Transmission Lines and Meta-Materials based on Quantum Hall Plasmonics
The characteristic impedance of a microwave transmission line is typically
constrained to a value = 50 , in-part because of the low
impedance of free space and the limited range of permittivity and permeability
realizable with conventional materials. Here we suggest the possibility of
constructing high-impedance transmission lines by exploiting the plasmonic
response of edge states associated with the quantum Hall effect in gated
devices. We analyze various implementations of quantum Hall transmission lines
based on distributed networks and lumped-element circuits, including a detailed
account of parasitic capacitance and Coulomb drag effects, which can modify
device performance. We additionally conceive of a meta-material structure
comprising arrays of quantum Hall droplets and analyze its unusual properties.
The realization of such structures holds promise for efficiently wiring-up
quantum circuits on chip, as well as engineering strong coupling between
semiconductor qubits and microwave photons
Detection and quantification of inverse spin Hall effect from spin pumping in permalloy/normal metal bilayers
Spin pumping is a mechanism that generates spin currents from ferromagnetic
resonance (FMR) over macroscopic interfacial areas, thereby enabling sensitive
detection of the inverse spin Hall effect that transforms spin into charge
currents in non-magnetic conductors. Here we study the spin-pumping-induced
voltages due to the inverse spin Hall effect in permalloy/normal metal bilayers
integrated into coplanar waveguides for different normal metals and as a
function of angle of the applied magnetic field direction, as well as microwave
frequency and power. We find good agreement between experimental data and a
theoretical model that includes contributions from anisotropic
magnetoresistance (AMR) and inverse spin Hall effect (ISHE). The analysis
provides consistent results over a wide range of experimental conditions as
long as the precise magnetization trajectory is taken into account. The spin
Hall angles for Pt, Pd, Au and Mo were determined with high precision to be
, , and ,
respectively.Comment: 11 page
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