标题： 高次谐波生成反映中红外电场下Mott转变的亚周期演化 显示英文标题

标题： High harmonic generation reflecting the sub-cycle evolution of the Mott transition under a mid-infrared electric field

摘要： 在强激光场中的固体表现出高次谐波生成（HHG），这可以提供关于弱关联系统中载流子动力学和能带结构的信息。 在强关联系统中，激光场可以通过载流子生成诱导出由电荷、自旋和轨道自由度纠缠形成的各种电子相之间的转变。 这一过程伴随的HHG应包含沿振荡场的非平衡电子态动力学信息——这一方面至今仍未解决。 在这里，我们表明一种强中红外（MIR）脉冲可以在一维铜氧化物Sr2CuO3中诱导莫特绝缘体-金属转变，其演化通过HHs的光谱特征体现出来。 当电场幅度超过6 MV/cm时，载流子被有效生成，每个谐波频率从MIR频率的奇数倍减少。 动力平均场理论表明，这些红移来源于在莫特绝缘体状态熔化过程中每个电场周期内的电子结构重构系列，这逐周期地修改了载流子复合的辐射相位。 这种现象在刚性带系统中可以忽略不计。 这项实验与理论研究证实，HH光谱学研究有可能揭示关联材料中非平衡相变的亚周期动力学。 显示英文摘要

摘要： Solids in an intense laser field show high-harmonic generation (HHG), which can provide information on carrier dynamics and band structures in weakly correlated systems. In strongly correlated systems, a laser field can induce a transition between the various electronic phases formed by the entanglement of charge, spin, and orbital degrees of freedom via carrier generation. The HHG accompanying this process should contain information on the nonequilibrium electronic-state dynamics along the oscillating field - an aspect that remains unresolved to date. Here, we show that an intense mid-infrared (MIR) pulse induces a Mott insulator-metal transition in a one-dimensional cuprate, Sr2CuO3, the evolution of which is reflected by the spectral features of HHs. When the electric-field amplitude exceeds 6 MV/cm, carriers are efficiently generated and each harmonic frequency decreases from odd multiples of the MIR frequency. Dynamical mean-field theory indicates that these redshifts originate from a series of electronic-structure reconstructions in each electric-field cycle during the melting of the Mott-insulator state, which modifies the radiation phase from carrier recombination cycle-by-cycle. This phenomenon is negligible in rigid-band systems. This experimental-theoretical study confirms that HH spectroscopy research can potentially unravel the sub-cycle dynamics of nonequilibrium phase transitions in correlated materials.