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arXiv · 2510.01826

Ultrafast giant enhancement of second harmonic generation in a strongly correlated cobaltite

Yuchen Cui·Qiaomei Liu·Qiong Wu·Shuxiang Xu·Junhan Huang·Hao Wang·Rongsheng Li·Shanshan Han·Wei Xu·Li Du·Ming Lu·Chunmei Zhang·Shangfei Wu·Xinbo Wang·Tao Dong·Li Yue·Dong Wu·Nanlin Wang
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Abstract

In quantum materials, nonlinear optical responses are highly sensitive to electronic structure and many-body interactions. Probing and manipulating such nonlinear processes is a complex and subtle endeavor, yet it offers deep insights into emerging physics and functionalities. Here, we report an anomalous ultrafast enhancement of second harmonic generation (SHG) in a strongly correlated cobaltite YbBaCo$_4$O$_7$. Above-bandgap femtosecond pumping increases SHG intensity by up to 60 % within 200 fs, with the enhancement persisting for tens of picoseconds. The enhancement is strongly anisotropic, with substantial amplification of in-plane susceptibility tensors, whereas the out-of-plane counterpart shows negligible change. We attribute these anomalies to ultrafast photodoping-induced modulation of the on-site Coulomb repulsion, which dynamically renormalizes the band structure and selectively amplifies specific $\chi^{(2)}$ components. These nonlinear dynamics encode rich information about the orbital symmetries and energies of the states involved, opening new avenues for all-optical probing of electronic structure in strongly correlated materials.

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Yuchen Cui, Qiaomei Liu, Qiong Wu, Shuxiang Xu, Junhan Huang, Hao Wang, Rongsheng Li, Shanshan Han, Wei Xu, Li Du, Ming Lu, Chunmei Zhang, Shangfei Wu, Xinbo Wang, Tao Dong, Li Yue, Dong Wu, Nanlin Wang. 2025-10-02. Ultrafast giant enhancement of second harmonic generation in a strongly correlated cobaltite. https://arxiv.org/abs/2510.01826

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