786 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
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
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
Superconducting properties of sulfur-doped iron selenide
The recent discovery of high-temperature superconductivity in single-layer
iron selenide has generated significant experimental interest for optimizing
the superconducting properties of iron-based superconductors through the
lattice modification. For simulating the similar effect by changing the
chemical composition due to S doping, we investigate the superconducting
properties of high-quality single crystals of FeSeS (=0, 0.04,
0.09, and 0.11) using magnetization, resistivity, the London penetration depth,
and low temperature specific heat measurements. We show that the introduction
of S to FeSe enhances the superconducting transition temperature ,
anisotropy, upper critical field , and critical current density
. The upper critical field and its anisotropy are strongly
temperature dependent, indicating a multiband superconductivity in this system.
Through the measurements and analysis of the London penetration depth and specific heat, we show clear evidence for strong coupling two-gap
-wave superconductivity. The temperature-dependence of
calculated from the lower critical field and electronic specific heat can be
well described by using a two-band model with -wave-like gaps. We find that
a -wave and single-gap BCS theory under the weak-coupling approach can not
describe our experiments. The change of specific heat induced by the magnetic
field can be understood only in terms of multiband superconductivity.Comment: 13 pages, 7 figure
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