7,382 research outputs found
Large Magnetic Susceptibility Anisotropy of Metallic Carbon Nanotubes
Through magnetic linear dichroism spectroscopy, the magnetic susceptibility
anisotropy of metallic single-walled carbon nanotubes has been extracted and
found to be 2-4 times greater than values for semiconducting single-walled
carbon nanotubes. This large anisotropy is consistent with our calculations and
can be understood in terms of large orbital paramagnetism of electrons in
metallic nanotubes arising from the Aharonov-Bohm-phase-induced gap opening in
a parallel field. We also compare our values with previous work for
semiconducting nanotubes, which confirm a break from the prediction that the
magnetic susceptibility anisotropy increases linearly with the diameter.Comment: 4 pages, 4 figure
Dynamics of the vortex-particle complexes bound to the free surface of superfluid helium
We present an experimental and theoretical study of the 2D dynamics of
electrically charged nanoparticles trapped under a free surface of superfluid
helium in a static vertical electric field. We focus on the dynamics of
particles driven by the interaction with quantized vortices terminating at the
free surface. We identify two types of particle trajectories and the associated
vortex structures: vertical linear vortices pinned at the bottom of the
container and half-ring vortices travelling along the free surface of the
liquid
Dynamics of fine particles due to quantized vortices on the surface of superfluid He
Peculiar dynamics of a free surface of the superfluid 4He has been observed
experimentally with a newly established technique utilizing a number of
electrically charged fine metal particles trapped electrically at the surface
by Moroshkin et al. They have reported that some portion of the particles
exhibit some irregular motions and suggested the existence of quantized
vortices interacting with the metal particles. We have conducted calculations
with the vortex filament model, which turns out to support the idea of the
vortex-particle interactions. The observed anomalous metal particle motions are
roughly categorized into two types; (1) circular motions with specific
frequencies, and (2) quasi-linear oscillations. The former ones seem to be
explained once we consider a vertical vortex filament whose edges are
terminated at the bottom and at a particle trapped at the surface. Although it
is not yet clear whether all the anomalous motions are due to the quantum
vortices, the vortices seem to play important roles for the motions.Comment: 7 pages, 10 figure
Zero-phonon lines in the spectra of dysprosium atoms in superfluid helium
We present an experimental study of a zero-phonon line (ZPL) in the
absorption spectrum of Dy atoms solvated in superfluid He. The dopants reside
in nanometer-sized spherical cavities known as atomic bubbles. We observe a
temperature-dependent broadening of ZPL in the absorption spectrum. The effect
is attributed to the scattering of thermal phonons on the atomic bubble that
leads to the dephasing of the Dy transition dipole. The extrapolated ZPL
intrinsic spectral width at zero temperature is 2300 times larger than the
natural linewidth in a free atom. This can be assigned to a fast radiationless
quenching of the upper state of the studied transition
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