Nonlinear phenomena in timedependent densityfunctional theory: What Rabi oscillations can teach us
Abstract
Through the exact solution of a twoelectron singlet system interacting with a monochromatic laser we prove that all adiabatic density functionals within timedependent densityfunctional theory are not able to discern between resonant and nonresonant (detuned) Rabi oscillations. This is rationalized in terms of a fictitious dynamical exchangecorrelation (xc) detuning of the resonance while the laser is acting. The nonlinear dynamics of the KohnSham system shows the characteristic features of detuned Rabi oscillations even if the exact resonant frequency is used. We identify the source of this error in a contribution from the xc functional to the set of nonlinear equations that describes the electron dynamics in an effective twolevel system. The constraint of preventing the detuning introduces a new strong condition to be satisfied by approximate xc functionals.
 Publication:

Physical Review B
 Pub Date:
 August 2011
 DOI:
 10.1103/PhysRevB.84.075107
 arXiv:
 arXiv:1101.2880
 Bibcode:
 2011PhRvB..84g5107F
 Keywords:

 71.15.Mb;
 42.65.k;
 71.10.w;
 Density functional theory local density approximation gradient and other corrections;
 Nonlinear optics;
 Theories and models of manyelectron systems;
 Condensed Matter  Other Condensed Matter
 EPrint:
 Phys. Rev. B 84, 075107 (2011)