712 research outputs found
Metal-Insulator Transition in 2D: Experimental Test of the Two-Parameter Scaling
We report a detailed scaling analysis of resistivity \rho(T,n) measured for
several high-mobility 2D electron systems in the vicinity of the 2D
metal-insulator transition. We analyzed the data using the two parameter
scaling approach and general scaling ideas. This enables us to determine the
critical electron density, two critical indices, and temperature dependence for
the separatrix in the self-consistent manner. In addition, we reconstruct the
empirical scaling function describing a two-parameter surface which fits well
the \rho(T,n) data.Comment: 4 pages, 4 figures, 1 tabl
Detection of mechanical resonance of a single-electron transistor by direct current
We have suspended an Al based single-electron transistor whose island can
resonate freely between the source and drain leads forming the clamps. In
addition to the regular side gate, a bottom gate with a larger capacitance to
the SET island is placed underneath to increase the SET coupling to mechanical
motion. The device can be considered as a doubly clamped Al beam that can
transduce mechanical vibrations into variations of the SET current. Our
simulations based on the orthodox model, with the SET parameters estimated from
the experiment, reproduce the observed transport characteristics in detail.Comment: 4 pages, 3 figure
Renormalization of hole-hole interaction at decreasing Drude conductivity
The diffusion contribution of the hole-hole interaction to the conductivity
is analyzed in gated GaAs/InGaAs/GaAs heterostructures. We show
that the change of the interaction correction to the conductivity with the
decreasing Drude conductivity results both from the compensation of the singlet
and triplet channels and from the arising prefactor in the
conventional expression for the interaction correction.Comment: 6 pages, 5 figure
Electronic structure, magnetic and optical properties of intermetallic compounds R2Fe17 (R=Pr,Gd)
In this paper we report comprehensive experimental and theoretical
investigation of magnetic and electronic properties of the intermetallic
compounds Pr2Fe17 and Gd2Fe17. For the first time electronic structure of these
two systems was probed by optical measurements in the spectral range of 0.22-15
micrometers. On top of that charge carriers parameters (plasma frequency and
relaxation frequency) and optical conductivity s(w) were determined.
Self-consistent spin-resolved bandstructure calculations within the
conventional LSDA+U method were performed. Theoretical interpetation of the
experimental s(w) dispersions indicates transitions between 3d and 4p states of
Fe ions to be the biggest ones. Qualitatively the line shape of the theoretical
optical conductivity coincides well with our experimental data. Calculated by
LSDA+U method magnetic moments per formula unit are found to be in good
agreement with observed experimental values of saturation magnetization.Comment: 16 pages, 5 figures, 1 tabl
Spin-splitting in the quantum Hall effect of disordered GaAs layers with strong overlap of the spin subbands
With minima in the diagonal conductance G_{xx} and in the absolute value of
the derivative |dG_{xy}/dB| at the Hall conductance value G_{xy}=e^{2}/h,
spin-splitting is observed in the quantum Hall effect of heavily Si-doped GaAs
layers with low electron mobility 2000 cm^2/Vs in spite of the fact that the
spin-splitting is much smaller than the level broadening. Experimental results
can be explained in the frame of the scaling theory of the quantum Hall effect,
applied independently to each of the two spin subbands.Comment: 4 pages, 4 figure
H-alpha Survey of the Local Volume: Isolated Southern Galaxies
We present our H-alpha observations of 11 isolated southern galaxies: SDIG,
PGC 51659, E 222-010, E 272-025, E 137-018, IC 4662, Sag DIG, IC 5052, IC 5152,
UGCA 438, and E149-003, with distances from 1 to 7 Mpc. We have determined the
total H-alpha fluxes from these galaxies. The star formation rates in these
galaxies range from 10^{-1} (IC 4662) to 10^{-4}_{\odot}/yr (SDIG) and the gas
depletion time at the observed star formation rates lies within the range from
1/6 to 24 Hubble times H_0^{-1} .Comment: 9 pages, 3 figure
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