3,458 research outputs found
Rethinking the relationship between voluntary associations, democratic citizenship, and cultural values
Collisional Dynamics of Half-Quantum Vortices in a Spinor Bose-Einstein Condensate
We present an experimental study on the interaction and dynamics of
half-quantum vortices (HQVs) in an antiferromagnetic spinor Bose-Einstein
condensate. By exploiting the orbit motion of a vortex dipole in a trapped
condensate, we perform a collision experiment of two HQV pairs, and observe
that the scattering motions of the HQVs is consistent with the short-range
vortex interaction that arises from nonsingular magnetized vortex cores. We
also investigate the relaxation dynamics of turbulent condensates containing
many HQVs, and demonstrate that spin wave excitations are generated by the
collisional motions of the HQVs. The short-range vortex interaction and the
HQV-magnon coupling represent two characteristics of the HQV dynamics in the
spinor superfluid.Comment: 7 pages, 6 figure
Observation of wall-vortex composite defects in a spinor Bose-Einstein condensate
We report the observation of spin domain walls bounded by half-quantum
vortices (HQVs) in a spin-1 Bose-Einstein condensate with antiferromagnetic
interactions. A spinor condensate is initially prepared in the easy-plane polar
phase, and then, suddenly quenched into the easy-axis polar phase. Domain walls
are created via the spontaneous symmetry breaking in the phase
transition and the walls dynamically split into composite defects due to snake
instability. The end points of the defects are identified as HQVs for the polar
order parameter and the mass supercurrent in their proximity is demonstrated
using Bragg scattering. In a strong quench regime, we observe that singly
charged quantum vortices are formed with the relaxation of free wall-vortex
composite defects. Our results demonstrate a nucleation mechanism for composite
defects via phase transition dynamics.Comment: 10 pages, 11 figures, reference update
Observation of a Geometric Hall Effect in a Spinor Bose-Einstein Condensate with a Skyrmion Spin Texture
For a spin-carrying particle moving in a spatially varying magnetic field,
effective electromagnetic forces can arise due to the geometric phase
associated with adiabatic spin rotation of the particle. We report the
observation of a geometric Hall effect in a spinor Bose-Einstein condensate
with a skyrmion spin texture. Under translational oscillations of the spin
texture, the condensate resonantly develops a circular motion in a harmonic
trap, demonstrating the existence of an effective Lorentz force. When the
condensate circulates, quantized vortices are nucleated in the boundary region
of the condensate and the vortex number increases over 100 without significant
heating. We attribute the vortex nucleation to the shearing effect of the
effective Lorentz force from the inhomogeneous effective magnetic field.Comment: 9 pages, 11 figure
Enhancing 2D Growth of Organic Semiconductor Thin Films with Macroporous Structures via a Small-Molecule Heterointerface
The physical structure of an organic solid is strongly affected by the surface of the underlying substrate. Controlling this interface is an important issue to improve device performance in the organic electronics community. Here we report an approach that utilizes an organic heterointerface to improve the crystallinity and control the morphology of an organic thin film. Pentacene is used as an active layer above, and m-bis(triphenylsilyl) benzene is used as the bottom layer. Sequential evaporations of these materials result in extraordinary morphology with far fewer grain boundaries and myriad nanometre-sized pores. These peculiar structures are formed by difference in molecular interactions between the organic layers and the substrate surface. The pentacene film exhibits high mobility up to 6.3 cm(2)V(-1)s(-1), and the pore-rich structure improves the sensitivity of organic-transistor-based chemical sensors. Our approach opens a new way for the fabrication of nanostructured semiconducting layers towards high-performance organic electronics.X116049Nsciescopu
A Typology of Organizational Behavior : At the Crossroad of Risk and Uncertainty
Four modes of organizational behavior are proposed by crossing two behavioral dimensions adopted from organizational ecology (inertia vs. change) and neoinstitutionalism (normative vs. deviant). Those four modes are innovative (deviant change), reformative (normative change), conservative (normative inertia), and reactionary (deviant inertia) modes in the life-cycle of organizational behavior. Also identified are two distributional characteristics underlying each behavioral dimension: low risk vs. high risk underlying inertia vs. change, and certainty vs. uncertainty underlying normative vs. deviant. Through the integration of inertia-conformity and risk-uncertainty dimensions, hypotheses are generated on how transition to the next mode can be either promoted or hindered by sociopolitical resources at the organizational level and by intervention of the state and the civil society at the societal level. The typology and hypotheses outlined in this paper aim to further theoretical articulation and empirical tests on the evolutionary dynamics of organizational forms and institutions in the market
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