Optical control of competing exchange interactions and coherent spin-charge coupling in two-orbital Mott insulators
Marion Barbeau, Martin Eckstein, Mikhail I. Katsnelson +1 more
In order to have a better understanding of ultrafast electrical control of exchange interactions in multi-orbital systems, we study a two-orbital Hubbard model at half filling under the action of a time-periodic electric field. Using suitable projection operators and a generalized time-dependent canonical transformation, we derive an effective Hamiltonian which describes two different regimes. First, for a wide range of non-resonant frequencies, we find a change of the bilinear Heisenberg exchange J_{\textrm{ex}} J ex that is analogous to the single-orbital case. Moreover we demonstrate that also the additional biquadratic exchange interaction B_{\textrm{ex}} B ex can be enhanced, reduced and even change sign depending on the electric field. Second, for special driving frequencies, we demonstrate a novel spin-charge coupling phenomenon enabling coherent transfer between spin and charge degrees of freedom of doubly ionized states. These results are confirmed by an exact time-evolution of the full two-orbital Mott-Hubbard Hamiltonian.
arXiv:1803.03796•SciPost Physics•Mar 5, 2019•16 citations