Adiabatic approximation in nonperturbative time-dependent density-functional theory.
We construct the exact exchange-correlation potential of time-dependent density-functional theory and the approximation to it that is adiabatic but exact otherwise. For the strong-field double ionization of the Helium atom these two potentials are virtually identical. Thus, memory effects play a negligible role in this paradigm process of nonlinear, nonperturbative electron dynamics. We identify the regime of high-frequency excitations where the adiabatic approximation breaks down and explicitly calculate the nonadiabatic contribution to the exchange-correlation potential.
Physikalisches Institut, Universität Bayreuth, Bayreuth, Germany.
M
M
Thiele
E K U
EK
Gross
S
S
Kümmel