13 research outputs found
Tunneling in a cavity
The mechanism of coherent destruction of tunneling found by Grossmann et al.
[Phys. Rev. Lett. 67, 516 (1991)] is studied from the viewpoint of quantum
optics by considering the photon statistics of a single mode cavity field which
is strongly coupled to a two-level tunneling system (TS). As a function of the
interaction time between TS and cavity the photon statistics displays the
tunneling dynamics. In the semi-classical limit of high photon occupation
number , coherent destruction of tunneling is exhibited in a slowing down of
an amplitude modulation for certain parameter ratios of the field. The
phenomenon is explained as arising from interference between displaced number
states in phase space which survives the large limit due to identical
scaling between orbit width and displacement.Comment: 4 pages Revtex, 2 PS-figures, appears in The Physical Review
Driving-Induced Symmetry Breaking in the Spin-Boson System
A symmetric dissipative two-state system is asymptotically completely
delocalized independent of the initial state. We show that driving-induced
localization at long times can take place when both the bias and tunneling
coupling energy are harmonically modulated. Dynamical symmetry breaking on
average occurs when the driving frequencies are odd multiples of some reference
frequency. This effect is universal, as it is independent of the dissipative
mechanism. Possible candidates for an experimental observation are flux
tunneling in the variable barrier rf SQUID and magnetization tunneling in
magnetic molecular clusters.Comment: 4 pages, 4 figures, to be published in PR
Driven Tunneling Dynamics: Bloch-Redfield Theory versus Path Integral Approach
In the regime of weak bath coupling and low temperature we demonstrate
numerically for the spin-boson dynamics the equivalence between two widely used
but seemingly different roads of approximation, namely the path integral
approach and the Bloch-Redfield theory. The excellent agreement between these
two methods is corroborated by a novel efficient analytical high-frequency
approach: it well approximates the decay of quantum coherence via a series of
damped coherent oscillations. Moreover, a suitably tuned control field can
selectively enhance or suppress quantum coherence.Comment: 4 pages including 3 figures, submitted for publicatio
Analytical solutions to the third-harmonic generation in trans-polyacetylene: Application of dipole-dipole correlation on the single electron models
The analytical solutions for the third-harmonic generation (THG) on infinite
chains in both Su-Shrieffer-Heeger (SSH) and Takayama-Lin-Liu-Maki (TLM) models
of trans-polyacetylene are obtained through the scheme of dipole-dipole ()
correlation. They are not equivalent to the results obtained through static
current-current () correlation or under polarization operator
. The van Hove singularity disappears exactly in the analytical forms,
showing that the experimentally observed two-photon absorption peak (TPA) in
THG may not be directly explained by the single electron models.Comment: 10 pages, 4 figures, submitted to Phys. Rev.