11 research outputs found
Peak Values of Conductivity in Integer and Fractional Quantum Hall Effect
The diagonal conductivity was measured in the Corbino geometry
in both integer and fractional quantum Hall effect (QHE). We find that peak
values of are approximately equal for transitions in a wide range
of integer filling factors , as expected in scaling theories of QHE.
This fact allows us to compare peak values in the integer and fractional
regimes within the framework of the law of corresponding states.Comment: 8 pages (revtex format), 3 postscript figure
Non Linear Current Response of a Many-Level Tunneling System: Higher Harmonics Generation
The fully nonlinear response of a many-level tunneling system to a strong
alternating field of high frequency is studied in terms of the
Schwinger-Keldysh nonequilibrium Green functions. The nonlinear time dependent
tunneling current is calculated exactly and its resonance structure is
elucidated. In particular, it is shown that under certain reasonable conditions
on the physical parameters, the Fourier component is sharply peaked at
, where is the spacing between
two levels. This frequency multiplication results from the highly nonlinear
process of photon absorption (or emission) by the tunneling system. It is
also conjectured that this effect (which so far is studied mainly in the
context of nonlinear optics) might be experimentally feasible.Comment: 28 pages, LaTex, 7 figures are available upon request from
[email protected], submitted to Phys.Rev.
Vibration-assisted electron tunneling in C140 transistors
We measure electron tunneling in transistors made from C140, a molecule with a mass-spring-mass geometry chosen as a model system to study electron-vibration coupling. We observe vibration-assisted tunneling at an energy corresponding to the stretching mode of C140. Molecular modeling provides explanations for why this mode couples more strongly to electron tunneling than to the other internal modes of the molecule. We make comparisons between the observed tunneling rates and those expected from the Franck-Condon model.Validerad; 2005; 20061110 (ysko