1,117 research outputs found
Electrical Tuning of Single Nitrogen-Vacancy Center Optical Transitions Enhanced by Photoinduced Fields
We demonstrate precise control over the zero-phonon optical transition
energies of individual nitrogen-vacancy (NV) centers in diamond by applying
multiaxis electric fields, via the dc Stark effect. The Stark shifts display
surprising asymmetries that we attribute to an enhancement and rectification of
the local electric field by photoionized charge traps in the diamond. Using
this effect, we tune the excited-state orbitals of strained NV centers to
degeneracy and vary the resulting degenerate optical transition frequency by
>10 GHz, a scale comparable to the inhomogeneous frequency distribution. This
technique will facilitate the integration of NV-center spins within photonic
networks.Comment: 10 pages, 6 figure
Phonon driven spin distribution due to the spin-Seebeck effect
Here we report on measurements of the spin-Seebeck effect of GaMnAs over an
extended temperature range alongside the thermal conductivity, specific heat,
magnetization, and thermoelectric power. The amplitude of the spin-Seebeck
effect in GaMnAs scales with the thermal conductivity of the GaAs substrate and
the phonon-drag contribution to the thermoelectric power of the GaMnAs,
demonstrating that phonons drive the spin redistribution. A phenomenological
model involving phonon-magnon drag explains the spatial and temperature
dependence of the measured spin distribution.Comment: 12 pages, 3 figure
Long dephasing time and high temperature ballistic transport in an InGaAs open quantum dot
We report on measurements of the magnetoconductance of an open circular
InGaAs quantum dot between 1.3K and 204K. We observe two types of
magnetoconductance fluctuations: universal conductance fluctuations (UCFs), and
'focusing' fluctuations related to ballistic trajectories between openings. The
electron phase coherence time extracted from UCFs amplitude is larger than in
GaAs/AlGaAs quantum dots and follows a similar temperature dependence (between
T^-1 and T^-2). Below 150K, the characteristic length associated with
'focusing' fluctuations shows a slightly different temperature dependence from
that of the conductivity.Comment: 6 pages, 4 figures, proceedings of ICSNN2002, to appear in Physica
Charge Transport Properties of a Metal-free Phthalocyanine Discotic Liquid Crystal
Discotic liquid crystals can self-align to form one-dimensional
semiconducting wires, many tens of microns long. In this letter, we describe
the preparation of semiconducting films where the stacking direction of the
disc-like molecules is perpendicular to the substrate surface. We present
measurements of the charge carrier mobility, applying temperature-dependent
time-of-flight transient photoconductivity, space-charge limited current
measurements, and field-effect mobility measurements. We provide experimental
verification of the highly anisotropic nature of semiconducting films of
discotic liquid crystals, with charge carrier mobilities of up to
2.8x10cm/Vs. These properties make discotics an interesting choice
for applications such as organic photovoltaics.Comment: 5 pages, 5 figure
Thermopower and thermal conductivity in the Weyl semimetal NbP
The Weyl semimetal NbP exhibits an extremely large magnetoresistance (MR) and
an ultra-high mobility. The large MR originates from a combination of the
nearly perfect compensation between electron- and hole-type charge carriers and
the high mobility, which is relevant to the topological band structure. In this
work we report on temperature- and field-dependent thermopower and thermal
conductivity experiments on NbP. Additionally, we carried out complementary
heat capacity, magnetization, and electrical resistivity measurements. We found
a giant adiabatic magnetothermopower with a maximum of 800 V/K at 50 K in
a field of 9 T. Such large effects have been observed rarely in bulk materials.
We suggest that the origin of this effect might be related to the high
charge-carrier mobility. We further observe pronounced quantum oscillations in
both thermal conductivity and thermopower. The obtained frequencies compare
well with our heat capacity and magnetization data.Comment: 6 pages, 3 figure
ASSOCIATION OF LACTOFERRIN WITH SPECIFIC GRANULES IN RABBIT HETEROPHIL LEUKOCYTES
Lactoferrin has been identified in rabbit heterophil leukocytes on the basis of its immunological reactivity, electrophoretic mobility, acid-resistant iron-binding properties, and spectral characteristics. Leukocyte lactoferrin was found to be exclusively localized in the specific (secondary) granules, which have been resolved from other subcellular components by zonal differential centrifugation and by isopycnic equilibration
Atomic Layer Deposition Nucleation Dependence on Diamond Surface Termination
Surface termination and interfacial interactions are critical for advanced
solid-state quantum applications. In this paper, we demonstrate that atomic
layer deposition (ALD) can both provide valuable insight on the chemical
environment of the surface, having sufficient sensitivity to distinguish
between the common diamond (001) surface termination types and passivate these
interfaces as desired. We selected diamond substrates exhibiting both smooth
and anomalously rough surfaces to probe the effect of morphology on ALD
nucleation. We use high resolution in situ spectroscopic ellipsometry to
monitor the surface reaction with sub-angstrom resolution, to evaluate the
nucleation of an ALD Al2O3 process as a function of different ex and in situ
treatments to the diamond surface. In situ water dosing and high vacuum
annealing provided the most favorable environment for nucleation of
dimethylaluminum isopropoxide and water ALD. Hydrogen termination passivated
both smooth and rough surfaces while triacid cleaning passivated the smooth
surface only, with striking effectiveness.Comment: 31 pages, 14 figure
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