Nonlinear phenomena in time-dependent density-functional theory: What Rabi oscillations can teach us
Abstract
Through the exact solution of a two-electron singlet system interacting with a monochromatic laser we prove that all adiabatic density functionals within time-dependent density-functional theory are not able to discern between resonant and nonresonant (detuned) Rabi oscillations. This is rationalized in terms of a fictitious dynamical exchange-correlation (xc) detuning of the resonance while the laser is acting. The nonlinear dynamics of the Kohn-Sham 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 two-level 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 many-electron systems;
- Condensed Matter - Other Condensed Matter
- E-Print:
- Phys. Rev. B 84, 075107 (2011)