Spin-orbit mixed states in an electromagnetic field

Motivated by our recent discovery of large gyrotropic signals in some Jahn-Teller manganites [1], we explore the interaction of light with spin-mixed states in 3d metals. We show that spin-orbit mixing enables electronic transitions that are sensitive to circularly polarized light, giving rise to a gyrotropic response. Such interactions offer the opportunity to use light to entangle orbital and spin degrees of freedom. We find that, in addition to spin-orbit coupling, Jahn-Teller interactions are relevant to enhance the observed optical gyrotropy in solid-state 3d systems. Our approach, which includes a group-theoretic treatment of spin-orbit coupling, has wide applicability and provides a versatile tool to explore the interaction of electromagnetic fields with electronic states in transition metals with arbitrary spin-orbit coupling strength and point-group symmetries [2]. Ultrafast pump-probe experiments further confirm that the optical properties of the Janh-Teller manganites can be described completely in terms of a two polaron mode model, and allow us to extract the lifetime of the excitations and the role of oxygen mediated inter-site hopping.



[1] B. Casals et al., Phys. Rev. Lett. 117, 026401 (2016).

[2] A. S. Miñarro and G. Herranz, Phys. Rev. B 106, 165108 (2022).