AI 中文总结
本研究通过旋转各向异性二次谐波产生证明电子掺杂钛酸锶的铁电相变具有序-无序本质，且飞秒光场可超快可逆操控其极性纳米区，建立了极性金属的全光操控途径。
AI 中文摘要
电子掺杂钛酸锶已成为典型的量子铁电金属，为探究铁电不稳定性与巡游电子交织如何产生包括非常规超导在内的量子现象提供了良好平台。尽管已有大量研究，但铁电相变的微观起源仍未明确，存在基于软模驱动的位移机制与局部偶极子有序-无序排列的不同解释。特别是，局部偶极子形成纳米级空间异质团簇，称为极性纳米区，这对探测或操控它们构成重大挑战。本研究采用旋转各向异性二次谐波产生（一种对称分辨探针），定量分析稀电子掺杂Sr₀.₉₅Ba₀.₀₅Ti₁₋ₓNbₓO₃中极性纳米区的取向统计。通过追踪热循环中极性纳米区的排列与熔解，明确证明铁电相变的有序-无序本质。进一步研究表明，在相变温度以上，飞秒光场可对原本无序的极性纳米区实现确定性操控，在超快时间尺度上实现极性织构的可逆写入与读出。本研究结果为铁电不稳定性提供了新见解，并建立了在常规电学方法不可行的极性金属系统中全光操控的途径。
英文摘要
Electron-doped strontium titanate has emerged as a prototypical quantum ferroelectric metal. It provides a fertile ground to explore how ferroelectric instability intertwined with itinerant electrons creates quantum phenomena, including unconventional superconductivity. Despite extensive studies, the microscopic origin of the ferroelectric transition remains unsettled, with distinct interpretations based on displacive mechanism driven by soft mode and order-disorder alignment of local dipoles. In particular, the local dipoles form nanoscale, spatially heterogeneous clusters, termed polar nanoregions, posing a significant challenge for probing or manipulating them. Here, using rotational anisotropy second harmonic generation, a symmetry-resolved probe, we quantify the orientational statistics of polar nanoregions in dilute electron-doped Sr$_{0.95}$Ba$_{0.05}$Ti$_{1-x}$Nb$_x$O$_3$. By tracking the alignment and meltdown of polar nanoregions in thermal cycles, we unambiguously demonstrate the order-disorder nature of the ferroelectric transition. We further show that, above transition temperature, femtosecond optical fields enable deterministic control of otherwise disordered polar nanoregions, realizing reversible write and readout of polar textures on ultrafast timescales. Our findings provide new insight into ferroelectric instability and establish an all-optical route of controlling polar metal systems where conventional electrical approaches are not feasible.
