115 research outputs found
Classical and Quantum Dynamics of a Periodically Driven Particle in a Triangular Well
We investigate the correspondence between classical and quantum mechanics for
periodically time dependent Hamiltonian systems, using the example of a
periodically forced particle in a one-dimensional triangular well potential. In
particular, we consider quantum mechanical Floquet states associated with
resonances in the classical phase space. When the classical motion exhibits
{\it sub}harmonic resonances, the corresponding Floquet states maintain the
driving field's periodicity through dynamical tunneling. This principle applies
both to Floquet states associated with classical invariant vortex tubes
surrounding stable, elliptic periodic orbits and to Floquet states that are
associated with unstable, hyperbolic periodic orbits. The triangular well model
also poses a yet unsolved mathematical problem, related to perturbation theory
for systems with a dense pure point spectrum. The present approximate
analytical and numerical results indicate that quantum tunneling between
different resonance zones is of crucial importance for the question whether the
driven triangular well has a dense point or an absolutely continuous
quasienergy spectrum, or whether there is a transition from the one to the
other.Comment: revtex, 36 pages, 18 figures (available upon request), to appear in
Annals of Physic
Electric-field control of a hydrogenic donor's spin in a semiconductor
An AC electric field applied to a donor-bound electron in a semiconductor
modulates the orbital character of its wave function, which affects the
electron's spin dynamics via the spin-orbit interaction. Numerical calculations
of the spin dynamics of a hydrogenic donor (Si) embedded in GaAs, using a
real-space multi-band k.p formalism, show the high symmetry of the hydrogenic
donor state results in strongly nonlinear dependences of the electronic g
tensor on applied fields. A nontrivial consequence is that the most rapid Rabi
oscillations occur for electric fields modulated at a subharmonic of the Larmor
frequency
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