Ultrafast giant enhancement of second harmonic generation in a strongly correlated cobaltite YbBaCo4O7
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
公開日: 2025/10/2
Abstract
We report the observation of ultrafast photoinduced giant enhancement of optical second harmonic generation (SHG) efficiency in cobaltite YbBaCo4O7. Upon femtosecond pumping at energies above the band gap, the system exhibits an ultrafast enhancement in SHG intensity, reaching up to 60% higher than the initial value, then decays into a metastable state maintaining the enhancement. The enhancement scales linearly with pump fluence but shows no dependence on pump polarization. A pure electronic process sets in within the first ~200 fs and is accompanied by a pronounced anisotropic amplification of nonlinear susceptibility. We propose this anomalous SHG enhancement originates from ultrafast electronic band renormalization arising from dynamical modification of multi-electron correlations. In stark contrast to conventional asymmetric systems where SHG is typically suppressed upon photoexcitation, our experimental findings shed a new light on ultrafast optical control nonlinear properties in quantum materials.