Search results for "Single"
showing 10 items of 4920 documents
Dynamics of topological spin structures
2015
Topological spin structures that emerge from the Dzyaloshinskii-Moriya interaction (DMI), such as chiral domain walls and skyrmions have become the focus of intense investigations due to exciting physics and possible applications [1].
Experimental determination of single molecule toroic behaviour in a Dy8 single molecule magnet
2019
The enhancement of toroic motifs through coupling toroidal moments within molecular nanomagnets is a new, interesting and relevant approach for both fundamental research and potential quantum computation applications. We investigate a Dy8 molecular cluster and discover it has a antiferrotoroic ground state with slow magnetic relaxation. The experimental characterization of the magnetic anisotropy axes of each magnetic center and their exchange interactions represents a considerable challenge due to the non-magnetic nature of the toroidal motif. To overcome this and obtain access to the low energy states of Dy8 we establish a multi-orientation single-crystal micro Hall sensor magnetometry ap…
Some Properties of Massless Particles in Arbitrary Dimensions
1998
Various properties of two kinds of massless representations of the n-conformal (or (n+1)-De Sitter) group [Formula: see text] are investigated for n≥2. It is found that, for space-time dimensions n≥3, the situation is quite similar to the one of the n=4 case for Sn-massless representations of the n-De Sitter group [Formula: see text]. These representations are the restrictions of the singletons of [Formula: see text]. The main difference is that they are not contained in the tensor product of two UIRs with the same sign of energy when n>4, whereas it is the case for another kind of massless representations. Finally some examples of Gupta–Bleuler triplets are given for arbitrary spin and…
Ground-state properties of generalized Heisenberg chains with composite spin.
1988
We consider in detail the ground-state properties of recently introduced generalized Heisenberg models which can have several spin operators at each site and which interpolate smoothly between Heisenberg chains of different spin lengths. We show that the mappings to field-theoretical models used to describe the critical properties of the Heisenberg model remain valid in the composite-spin model. In models which interpolate between the spin-(1/2 and the spin-1 behavior, these mappings predict an extended singlet phase around the isotropic antiferromagnetic point whenever the models move away from the spin-(1/2 point. Numerical calculations on finite chains seem to confirm the existence of th…
Measurement of theBs0Lifetime in the Exclusive Decay ChannelBs0→J/ψϕ
2005
Using the exclusive decay B-s(0)-->J/psi(mu(+)mu(-))phi(K+K-), we report the most precise single measurement of the B-s(0) lifetime. The data sample corresponds to an integrated luminosity of approximately 220 pb(-1) collected with the D0 detector at the Fermilab Tevatron Collider in 2002-2004. We reconstruct 337 signal candidates, from which we extract the B-s(0) lifetime, tau(B-s(0))=1.444(-0.090)(+0.098)(stat)+/-0.020(sys) ps. We also report a measurement for the lifetime of the B-0 meson using the exclusive decay B-0-->J/psi(mu(+)mu(-))K-*0(892)(K(+)pi(-)). We reconstruct 1370 signal candidates, obtaining tau(B-0)=1.473(-0.050)(+0.052)(stat)+/-0.023(sys) ps, and the ratio of lifetimes, …
Generalized bloch equations for optical interactions in confined geometries
2005
By combining the field-susceptibility technique with the optical Bloch equations, a general formalism is developed for the investigation of molecular photophysical phenomena triggered by nanometer scale optical fields in the presence of complex environments. This formalism illustrate the influence of the illumination regime on the fluorescence signal emitted by a single molecule in a complex environment. In the saturated case, this signal is proportional to the optical local density of states, while it is proportional to the near-field intensity in the non-saturated case. (C) 2005 Elsevier B.V. All rights reserved.
Experiments on optical fiber interferometers and laser modes
1992
Three experiments on optical fiber interferometers, suitable for a teaching laboratory, are described. The guiding characteristics of single mode optical fibers enable simple interferometry experiments with large path differences to be carried out easily. These experiments show that the fringe visibility exhibits a periodic dependence on the path difference when using a multilongitudinal mode HeNe laser. A simple model can be used to explain this dependence in terms of the mode spectrum of the laser.
Vector description of higher-order modes in photonic crystal fibers
2000
We extensively study the propagation features of higher-order modes in a photonic crystal fiber (PCF). Our analysis is based on a full-vector modal technique specially adapted to accurately describe light propagation in PCF's. Unlike conventional fibers, PCF's exhibit a somewhat unusual mechanism for the generation of higher-order modes. Accordingly, PCF's are characterized by the constancy of the number of modes below a wavelength threshold. An explicit verification of this property is given through a complete analysis of the dispersion relations of higher-order modes in terms of the structural parameters of this kind of fiber. The transverse irradiance distributions for some of these high…
Observation of induced modulational polarization instabilities and pulse-train generation in the normal-dispersion regime of a birefringent optical f…
1998
Four-photon mixing in a low-birefringence fiber is strongly influenced by the orientation of the pump and signal waves with respect to the fiber axes. We experimentally investigated the dependence of the modulational gain spectra on pump power and polarization by mixing orthogonal pump and probe light beams in a birefringent optical fiber. With a pump on the fast fiber axis, a cascade of sidebands was generated in the regime of normal fiber dispersion. These sidebands are shown to correspond to 0.2–0.3-THz trains of pulses with complex polarization profiles. The analysis reveals that, at particular values of the input pump and probe powers and signal frequency detuning, trains of dark-solit…
Quantized separations of phase-locked soliton pairs in fiber lasers
2003
Quantized separations of phase-locked soliton pairs in fiber lasers were presented. The relation between the Kelly sidebands and the quantized separations between solitons was confirmed. Simulation results showed that the solitons can see each other at relatively larger distances than they would in the absence of radiation.