Ultrafast Mid Infrared Pump-Optical Kerr Probe of Correlated Mott-Hubbard Antiferromagnets*

We utilize intense ultrafast mid-infrared (mid-IR) circularly polarized pump pulses to preferentially excite spin degrees of freedom through coherent two-magnon excitation as measured via the magneto-optic Kerr effect using 800 nm pulses. Our previous results [1] on the spin-orbit coupled Mott-Hubbard insulator (MHI) Sr₂IrO₄ indicate that magnon generation using mid-IR pulses is nearly an order of magnitude more efficient in comparison to above gap doublon generation. To clarify the potential of mid-IR pulses for coherent magnon generation, we are investigating the canonical MHI nickel oxide which serves as a well characterized material for comparison with theoretical predictions [2]. This presentation will provide an update on these experiments with a view towards mode-selective spin excitation in quantum materials.
[1] Gu-Feng Zhang, Xiang Chen, Urban F.P. Seifert, Jingdi Zhang, Kevin Cremin, Leon Balents, Stephen D. Wilson and Richard D. Averitt. “Ultrafast magnetic control in a spin-orbit coupled iridate.” Manuscript in Preparation.
[2] Seifert, Urban FP, and Leon Balents. "Optical excitation of magnons in an easy-plane antiferromagnet: Application to Sr 2 IrO 4." Physical Review B 100, no. 12 (2019): 125161.