352 research outputs found
Spin Hall Effect and Spin Orbit coupling in Ballistic Nanojunctions
We propose a new scheme of spin filtering based on nanometric crossjunctions
in the presence of Spin Orbit interaction, employing ballistic nanojunctions
patterned in a two-dimensional electron gas. We demonstrate that the flow of a
longitudinal unpolarized current through a ballistic X junction patterned in a
two-dimensional electron gas with Spin Orbit coupling (SOC) induces a spin
accumulation which has opposite signs for the two lateral probes. This spin
accumulation, corresponding to a transverse pure spin current flowing in the
junction, is the main observable signature of the spin Hall effect in such
nanostructures.
We benchmark the effects of two different kinds of Spin Orbit interactions.
The first one (-SOC) is due to the interface electric field that
confines electrons to a two-dimensional layer, whereas the second one
(-SOC) corresponds to the interaction generated by a lateral confining
potential.Comment: 6 pages, 3 figure
Tunable control of the bandwidth and frequency correlations of entangled photons
We demonstrate experimentally a new technique to control the bandwidth and
the type of frequency correlations (correlation, anticorrelation, and even
uncorrelation) of entangled photons generated by spontaneous parametric
downconversion. The method is based on the control of the group velocities of
the interacting waves. This technique can be applied in any nonlinear medium
and frequency band of interest. It is also demonstrated that this technique
helps enhance the quality of polarization entanglement even when femtosecond
pulses are used as a pump.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Let
Effective interactions between inclusions in complex fluids driven out of equilibrium
The concept of fluctuation-induced effective interactions is extended to
systems driven out of equilibrium. We compute the forces experienced by
macroscopic objects immersed in a soft material driven by external shaking
sources. We show that, in contrast with equilibrium Casimir forces induced by
thermal fluctuations, their sign, range and amplitude depends on specifics of
the shaking and can thus be tuned. We also comment upon the dispersion of these
shaking-induced forces, and discuss their potential application to phase
ordering in soft-materials.Comment: 10 pages, 8 figures, to appear in PR
Resonances and resonant frequencies for a class of nonlinear systems
Resonant phenomena for a class of nonlinear systems, which can be described by a SDOF model with a polynomial type nonlinear stiffness, are investigated using Nonlinear Output Frequency Response Functions (NOFRFs). The concepts of resonance and resonant frequencies are proposed for the first time for a class of nonlinear systems. The effects of damping on the resonances and resonant frequencies are also analyzed. These results produce a novel interpretation of energy transfer phenomena in this class of nonlinear systems and show how the damping effect influences the system resonant frequencies and amplitudes. The results are important for the design and fault diagnosis of mechanical systems and structures which can be described by the SDOF nonlinear model
Modified Combline Filter for A Compact Size
Bandpass filters are widely used in microwave systems. And miniaturized bandpass filters are required to reduce the cost of a wireless communication system. Therefore, many prototypes have been studied to meet this requirement. The conventional comb-line filter is one of the so many types of proposed size-reduced filters. In this thesis, we propose a modified comb-line filter using a combination of end shorted parallel coupled lines and lumped capacitors. Using the above structure, the electrical length of the parallel coupled lines in the modified comb-line filter, which determines the size of a comb-line filter, can be reduced to even a few degrees, resulting in a much smaller circuit area. Inter-stage connecting lines have been added to connect the neighboring resonators for the suppression of unwanted coupling. The designed comb-line filter also shows a wide upper stopband. Design equations and method will be fully explained in this thesis. Measured results of a fabricated filter centered at 400 MHz show good agreement with the theoretical predications.Chapter 1 Introduction = 1
1.1 An introduction to Comb-line filters = 2
1.2 Research Contents = 4
Chapter 2 Miniaturization of the Quarter-wavelength Transmission Line = 5
2.1 Introduction = 5
2.2 Size-reducing method of the λ/4 transmission line = 7
Chapter 3 Bandpass Filter Design Theory = 15
3.1 Introduction = 15
3.2 Size-reduced Bandpass filter = 16
Chapter 4 Fabrication and Measurement = 25
4.1 EM simulation using HFSS = 25
4.2 Fabrication and Measurement = 31
Chapter 5 Conclusion = 37
References = 38
Acknowledgement = 4
Frequency domain energy transfer properties of bilinear oscillators under harmonic loadings
In this paper, the energy transfer phenomenon of bilinear oscillators in the frequency domain is analyzed using the new concept of Nonlinear Output Frequency Response Functions (NOFRFs). The analysis provides insight into how new frequency generation can occur using bilinear oscillators, and reveals, for the first time, that it is the resonant frequencies of the NOFRFs that dominate the occurrence of this well-known nonlinear behaviour. The results are of significance for the design and fault diagnosis of mechanical systems and structures which can be described by a bilinear oscillator model
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