Interseries transitions between Rydberg excitons in Cu2O

Abstract

We investigate the infrared optical transitions between excitons of the yellow, green and blue series in the cuprous oxide Cu2O. We show that, in many cases, the dipole approximation is inadequate and, in particular, that it breaks down in yellow-blue transitions even for moderate principal quantum numbers of n ≈ 10. The interband matrix elements of the transition operator needed for the evaluation of the excitonic transition strengths are derived from known as well as from fitted band parameters.

Interseries dipole transitions from yellow to green excitons in cuprous oxide

“…The resulting transition strengths are of the same order of magnitude as those found in Ref. [16]. The strongest transition in Table II is from the 2P yellow exciton to the exciton state with energy E = 2.28895 eV, which is a 3D state.…”

“…As shown in Ref. [16], this condition breaks down for transitions between the yellow and green series starting at n 15 for counter-propagating pump and probe beams. Extending our investigations to this parameter range thus requires going beyond the dipole approximation.…”

“…We extended the calculations for the yellow-to-green interseries transitions performed in Ref. [16] by including the complex valence band structure. To properly take into account the associated coupling between the green exciton states and the yellow continuum, we used the complex-coordinate rotation method for the calculation of the green exciton resonances as described in Ref.…”

“…A perturbation theoretical analysis of Eq. ( 30) up to first order in p has already been performed previously [16], yielding n, σ, p|π|n , σ , p = m 0 u n,σ , 0…”

“…Motivated by the aim to identify promising experimentally accessible dipole transitions for the coherent manipulation of Rydberg excitons [13,14] and the generation of giant optical nonlinearities [15], interseries transitions between the yellow and green, respectively yellow and blue, exciton series have been investigated using a hydrogen-like model for the exciton interaction [16]. The interseries transitions, i.e., those between different exciton series, have the distinct advantage over intraseries transitions, i.e., transitions within a single exciton series, by providing a more accessible choice of interrogation wavelengths.…”