4 research outputs found
Weak coupling approximations in non-Markovian Transport
We study the transport properties of the Fano-Anderson model with a
Lorentzian-shaped density of states in one of the electronic reservoirs. We
explicitly show that the energy dependence of the density of states can cause
non-Markovian effects and that the non-Markovian master equation may fail if
these effects are strong. We evaluate the stationary current, the zero
frequency current noise and the occupation dynamics of the resonant level by
means of a quantum master equation approach within different approximation
schemes and compare the results to the exact solution obtained by scattering
theory and Green's functions.Comment: 9 pages, 6 figures; due to suggestions of a referee we have added an
appendix where our kernel is derived in detail; a few typos are correcte
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.