51 research outputs found
Quantum electrodynamics and photon-assisted tunnelling in long Josephson junctions
We describe the interaction between an electromagnetic field and a long
Josephson junction (JJ) driven by a dc current. We calculate the amplitudes of
emission and absorption of light via the creation and annihilation of quantized
Josephson plasma waves (JPWs). Both, the energies of JPW quanta and the
amplitudes of light absorption and emission, strongly depend on the junction's
length and can be tuned by an applied dc current. Moreover, photon-assisted
macroscopic quantum tunnelling in long Josephson junctions show resonances when
the frequency of the outside radiation coincides with the current-driven
eigenfrequencies of the quantized JPWs.Comment: 9 pages, 4 figure
Estimates for parameters and characteristics of the confining SU(3)-gluonic field in an -meson
The confinement mechanism proposed earlier by the author is applied to
estimate the possible parameters of the confining SU(3)-gluonic field in an
-meson. For this aim the electric form factor of an
-meson is nonperturbatively computed in an explicit analytic form.
The estimates obtained are also consistent with the width of the
electromagnetic decay . The corresponding estimates of
the gluon concentrations, electric and magnetic colour field strengths are also
adduced for the mentioned field at the scales of the meson under consideration.Comment: 20 pages, LaTe
Hole burning in a nanomechanical resonator coupled to a Cooper pair box
We propose a scheme to create holes in the statistical distribution of
excitations of a nanomechanical resonator. It employs a controllable coupling
between this system and a Cooper pair box. The success probability and the
fidelity are calculated and compared with those obtained in the atom-field
system via distinct schemes. As an application we show how to use the
hole-burning scheme to prepare (low excited) Fock states.Comment: 7 pages, 10 figure
Dynamic manipulation of mechanical resonators in the high amplitude regime through optical backaction
Cavity optomechanics enables active manipulation of mechanical resonators
through backaction cooling and amplification. This ability to control
mechanical motion with retarded optical forces has recently spurred a race
towards realizing a mechanical resonator in its quantum ground state. Here,
instead of quenching optomechanical motion, we demonstrate high amplitude
operation of nanomechanical resonators by utilizing a highly efficient phonon
generation process. In this regime, the nanomechanical resonators gain
sufficient energy from the optical field to overcome the large energy barrier
of a double well potential, leading to nanomechanical slow-down and zero
frequency singularity, as predicted by early theories . Besides fundamental
studies and interests in parametric amplification of small forces,
optomechanical backaction is also projected to open new windows for studying
discrete mechanical states, and to foster applications. Here we realize a
non-volatile mechanical memory element, in which bits are written and reset via
optomechanical backaction by controlling the mechanical damping across the
barrier. Our study casts a new perspective on the energy dynamics in coupled
mechanical resonator - cavity systems and enables novel functional devices that
utilize the principles of cavity optomechanics.Comment: 22 pages, 5 figure
Experimentally realizable devices for domain wall motion control
Magnetic domain walls (MDWs) can move when driven by an applied magnetic field. This motion is important for numerous devices, including magnetic recording read/write heads, transformers and magnetic sensors. A magnetic film, with a sawtooth profile, localizes MDWs in discrete positions at the narrowest parts of the film. We propose a controllable way to move these domain walls between these discrete locations by applying magnetic field pulses. In our proposal, each applied magnetic pulse can produce an increment or step-motion for an MDW. This could be used as a shift register. A similarly patterned magnetic film attached to a large magnetic element at one end of the film operates as an XOR logic gate. The asymmetric sawtooth profile can be used as a ratchet resulting in either oscillating or running MDW motion, when driven by an ac magnetic field. Near a threshold drive (bistable point) separating these two dynamical regimes (oscillating and running MDW), a weak signal encoded in very weak oscillations of the external magnetic field drastically changes the velocity spectrum, greatly amplifying the mixing harmonics. This effect can be used either to amplify or shift the frequency of a weak signal.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/49053/2/njp5_1_082.pd
Magnetic field induced insulating phase in two-dimensional electron gas in InGaAs/InP: The Wigner solid
Activated Transport in Magnetic-Field Induced Insulating Phase in Two-Dimensional Electron Gas in InGaAs/InP Heterostructures
We report on experiments on low temperature (millikelvin range) activated magnetotransport on low-density two-dimensional electron systems in InGaAs/InP for Landau level filling factors 0.25 ≤ ν ≤ 0.55. The activation energy increases approximately linearly with decreasing filling factor. The observations are discussed in the light of the formation of the Wigner solid
Wigner Crystallization in InGaAs/InP Heterostructures with a Strong Disorder
Non-linear current-voltage characteristics were observed in the range of filling factors of 0.3 ≤ v ≤ 0.4 in a two-dimensional electron system in InGaAs/InP heterostructures with a strong disorder. The observations are explained qualitatively in terms of magnetic field induced localization and Wigner solidification
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