154 research outputs found
Anomalous time correlation in two-dimensional driven diffusive systems
We study the time correlation function of a density field in two-dimensional
driven diffusive systems within the framework of fluctuating hydrodynamics. It
is found that the time correlation exhibits power-law behavior in an
intermediate time regime in the case that the fluctuation-dissipation relation
is violated and that the power-law exponent depends on the extent of this
violation. We obtain this result by employing a renormalization group method to
treat a logarithmic divergence in time.Comment: 6 page
Quantitative analysis of electronic transport through weakly-coupled metal/organic interfaces
Using single-crystal transistors, we have performed a systematic experimental
study of electronic transport through oxidized copper/rubrene interfaces as a
function of temperature and bias. We find that the measurements can be
reproduced quantitatively in terms of the thermionic emission theory for
Schottky diodes, if the effect of the bias-induced barrier lowering is
included. Our analysis emphasizes the role of the coupling between metal and
molecules, which in our devices is weak due to the presence of an oxide layer
at the surface of the copper electrodes.Comment: 4 pages, 3 figure
Pressure screening in the interior of primary shells in double-wall carbon nanotubes
The pressure response of double-wall carbon nanotubes has been investigated
by means of Raman spectroscopy up to 10 GPa. The intensity of the radial
breathing modes of the outer tubes decreases rapidly but remain observable up
to 9 GPa, exhibiting a behavior similar (but less pronounced) to that of
single-wall carbon nanotubes, which undergo a shape distortion at higher
pressures. In addition, the tangential band of the external tubes broadens and
decreases in amplitude. The corresponding Raman features of the internal tubes
appear to be considerably less sensitive to pressure. All findings lead to the
conclusion that the outer tubes act as a protection shield for the inner tubes
whereas the latter increase the structural stability of the outer tubes upon
pressure application.Comment: PDF with 15 pages, 3 figures, 1 table; submitted to Physical Review
RVB Contribution to Superconductivity in
We view as electronically equivalent to (non-staggered) graphite
( layer) that has undergone a zero gap semiconductor to a superconductor
phase transition by a large c-axis (chemical) pressure due to layers.
Further, like the \ppi bonded planar organic molecules, graphite is an old
resonating valence bond (RVB) system. The RVB's are the `preexisting cooper
pairs' in the `parental' zero gap semiconducting (graphite) sheets that
manifests themselves as a superconducting ground state of the transformed
metal. Some consequences are pointed out.Comment: 4 pages, 2 figure, RevTex. Based on a talk given at the Institute
Seminar Week, IMSc, Madras (12-16, Feb. 2001
Ferromagnetism and giant magnetoresistance in the rare earth fullerides Eu6-xSrxC60
We have studied crystal structure, magnetism and electric transport
properties of a europium fulleride Eu6C60 and its Sr-substituted compounds,
Eu6-xSrxC60. They have a bcc structure, which is an isostructure of other M6C60
(M represents an alkali atom or an alkaline earth atom). Magnetic measurements
revealed that magnetic moment is ascribed to the divalent europium atom with S
= 7/2 spin, and a ferromagnetic transition was observed at TC = 10 - 14 K. In
Eu6C60, we also confirm the ferromagnetic transition by heat capacity
measurement. The striking feature in Eu6-xSrxC60} is very large negative
magnetoresistance at low temperature; the resistivity ratio \rho(H = 9
T)/\rho(H = 0 T) reaches almost 10^{-3} at 1 K in Eu6C60. Such large
magnetoresistance is the manifestation of a strong pi-f interaction between
conduction carriers on C60 and 4f electrons of Eu.Comment: 5 pages, 4 figure
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