Energy-Resolved Ultrafast Spectroscopic Investigation on the Spin-Coupled Electronic States in Multiferroic Hexagonal HoMnO₃

A complete temperature-dependent scheme of the Mn³⁺ on-site d-d transitions in multiferroic hexagonal HoMnO₃ (h-HoMnO₃) thin films was unveiled by energy-resolved ultrafast spectroscopy. The results unambiguously revealed that the ultrafast responses of the e_1g and e_2g states differed significantly in the hexagonal HoMnO₃. We demonstrated that the short-range antiferromagnetic and ferroelectric orderings are more relevant to the e_2g state, whereas the long-range antiferromagnetic ordering is intimately coupled to both the e_2g and e_1g states. Moreover, the primary thermalization times of the e_2g and e_1g states were 0.34 ± 0.08 ps and 0.38 ± 0.08 ps, respectively.