1,219 research outputs found
Detecting Spin-Polarized Currents in Ballistic Nanostructures
We demonstrate a mesoscopic spin polarizer/analyzer system that allows the
spin polarization of current from a quantum point contact in an in-plane
magnetic field to be measured. A transverse focusing geometry is used to couple
current from an emitter point contact into a collector point contact. At large
in-plane fields, with the point contacts biased to transmit only a single spin
(g < e^2/h), the voltage across the collector depends on the spin polarization
of the current incident on it. Spin polarizations of greater than 80% are found
for both emitter and collector at 300mK and 7T in-plane field.Comment: related papers at http://marcuslab.harvard.ed
How branching can change the conductance of ballistic semiconductor devices
We demonstrate that branching of the electron flow in semiconductor
nanostructures can strongly affect macroscopic transport quantities and can
significantly change their dependence on external parameters compared to the
ideal ballistic case even when the system size is much smaller than the mean
free path. In a corner-shaped ballistic device based on a GaAs/AlGaAs
two-dimensional electron gas we observe a splitting of the commensurability
peaks in the magnetoresistance curve. We show that a model which includes a
random disorder potential of the two-dimensional electron gas can account for
the random splitting of the peaks that result from the collimation of the
electron beam. The shape of the splitting depends on the particular realization
of the disorder potential. At the same time magnetic focusing peaks are largely
unaffected by the disorder potential.Comment: accepted for publication in Phys. Rev.
Isotopic-mass dependence of the A, B, and C excitonic band gaps in ZnO at low temperatures
Low temperature wavelength-modulated reflectivity measurements of isotopically engineered ZnO samples have yielded the dependence of their A, B, and C excitonic band gaps on the isotopic masses of Zn and O. The observed dependence is analyzed in terms of the band gap renormalization by zero-point vibrations via electron-phonon interaction and the volume dependence on isotopic mass. A simplified, two-oscillator model, employed in the analysis, yields zero-point renormalizations of the band gaps, -154 +/- 14 meV (A), -145 +/- 12 meV (B), and -169 +/- 14 meV (C), for ZnO with natural isotopic composition
Gramella portivictoriae sp nov, a novel member of the family Flavobacteriaceae isolated from marine sediment (vol 55, pg 2497, 2005)
A yellow-pigmented, Gram-negative, slowly gliding, rod-shaped, strictly aerobic bacterium
(UST040801-001T) was isolated from marine sediment. The DNA G+C content was 39?9 mol%.
The predominant fatty acids were a15 : 0, i15 : 0, i15 : 0 3-OH, i17 : 1v9c, i17 : 0 3-OH and
summed feature 3, comprising i15 : 0 2-OH and/or 16 : 1v7c (altogether representing 76?2% of
the total). MK-6 was the only respiratory quinone. Flexirubin-type pigments were not produced.
Phylogenetic analysis based on 16S rRNA gene sequences indicated that Gramella echinicola
KMM 6050T (the only species in the genus) was the closest relative of UST040801-001T,
sharing 98?0% sequence similarity. The DNA–DNA relatedness between UST040801-001T and
Gramella echinicola KMM 6050T was 13 %. Strain UST040801-001T can be distinguished
from G. echinicola by means of 11 phenotypic traits. The results of molecular and phenotypic
analyses suggested that UST040801-001T represents a novel species of Gramella. The name
Gramella portivictoriae sp. nov. is proposed for this bacterium, with UST040801-001T
(=NRRL 41137T=JCM 13192T) as the type strain
Current-Driven Magnetization Dynamics in Magnetic Multilayers
We develop a quantum analog of the classical spin-torque model for
current-driven magnetic dynamics. The current-driven magnetic excitation at
finite field becomes significantly incoherent. This excitation is described by
an effective magnetic temperature rather than a coherent precession as in the
spin-torque model. However, both the spin-torque and effective temperature
approximations give qualitatively similar switching diagrams in the
current-field coordinates, showing the need for detailed experiments to
establish the proper physical model for current-driven dynamics.Comment: 5 pages, 2 figure
Stenothermobacter spongiae gen. nov., sp. nov., a novel member of the family Flavobacteriaceae isolated from a marine sponge in the Bahamas, and emended description of Nonlabens tegetincola
A bacterial strain, UST030701-156T, was isolated from a marine sponge in the Bahamas. Strain UST030701-156T was orange-pigmented, Gram-negative, rod-shaped with tapered ends, slowly motile by gliding and strictly aerobic. The predominant fatty acids were a15 : 0, i15 : 0, i15 : 0 3-OH, i17 : 0 3-OH, i17 : 1ω9c and summed feature 3, comprising i15 : 0 2-OH and/or 16 : 1ω7c. MK-6 was the only respiratory quinone. Flexirubin-type pigments were not produced. Phylogenetic analysis based on 16S rRNA gene sequences placed UST030701-156T within a distinct lineage in the family Flavobacteriaceae, with 93·3 % sequence similarity to the nearest neighbour, Nonlabens tegetincola. The DNA G+C content of UST030701-156T was 41·0 mol% and was much higher than that of N. tegetincola (33·6 mol%). Strain UST030701-156T can be distinguished from other members of the Flavobacteriaceae by means of a number of chemotaxonomic and phenotypic characteristics. It is proposed, therefore, that UST030701-156T represents a novel taxon designated Stenothermobacter spongiae gen. nov., sp. nov. The type strain is UST030701-156T (=NRRL B-41138T=JCM 13191T). Carbon-source utilization by N. tegetincola was re-examined and an emended description is therefore included
- …