We use time- and energy-resolved optical spectroscopy to investigate the coupling of electron-hole excitations to the magnetic environment in the relativistic Mott insulator Na2IrO3. We show that, on the picosecond timescale, the photoinjected electron-hole pairs delocalize on the hexagons of the Ir lattice via the formation of quasi-molecular orbital (QMO) excitations and the exchange of energy with the short-range-ordered zig-zag magnetic background. The possibility of mapping the magnetic dynamics, which is characterized by typical frequencies in the THz range, onto high-energy (1-2 eV) charge excitations provides a new platform to investigate, and possibly control, the dynamics of magnetic interactions in correlated materials with strong spin-orbit coupling, even in the presence of complex magnetic phases.
@article{arxiv.1606.01667,
title = {Tracking local magnetic dynamics via high-energy charge excitations in a relativistic Mott insulator},
author = {Nicola Nembrini and Simone Peli and Francesco Banfi and Gabriele Ferrini and Yogesh Singh and Philipp Gegenwart and Riccardo Comin and Kateryna Foyevtsova and Andrea Damascelli and Adolfo Avella and Claudio Giannetti},
journal= {arXiv preprint arXiv:1606.01667},
year = {2016}
}