近日，美国加州理工学院的David Hsieh及其研究团队取得一项新进展。经过不懈努力，他们揭示多轨道莫特绝缘体中的时间隐藏磁序。相关研究成果已于2025年1月23日在国际知名学术期刊《自然—物理学》上发表。
该研究团队利用时间分辨的光学二次谐波产生和双折射测量技术，在光掺杂的Ca2RuO4中揭示了一种具有破缺滑移面对称性的亚稳态。研究人员发现，这种亚稳态出现在层内反铁磁序消失和光生载流子复合之后的很长时间。其性质与平衡相图中所有已知状态均不同，且与层内铁磁序相一致。
此外，模型哈密顿量计算表明，可以通过光掺杂访问这种状态的非热轨迹。这项研究结果将非平衡电子物质的探索空间扩展到了在中间时间尺度上出现的亚稳态。
据悉，光激发的量子材料可以被驱动进入热力学上无法达及的亚稳态，这些亚稳态展现出结构、电荷、自旋、拓扑和超导等序态。亚稳态通常在由内在电子和声子能量尺度决定的时间尺度上出现，范围从飞秒到皮秒，且能持续存在数周。因此，研究主要集中在超快或准静态极限情况下，而中间时间窗口则较少被探索。
附：英文原文
Title: Time-hidden magnetic order in a multi-orbital Mott insulator
Author: Li, Xinwei, Esin, Iliya, Han, Youngjoon, Liu, Yincheng, Zhao, Hengdi, Ning, Honglie, Barrett, Cora, Shan, Jun-Yi, Seyler, Kyle, Cao, Gang, Refael, Gil, Hsieh, David
Issue&Volume: 2025-01-23
Abstract: Photo-excited quantum materials can be driven into thermally inaccessible metastable states that exhibit structural, charge, spin, topological and superconducting orders. Metastable states typically emerge on timescales set by the intrinsic electronic and phononic energy scales, ranging from femtoseconds to picoseconds, and can persist for weeks. Therefore, studies have primarily focused on ultrafast or quasi-static limits, leaving the intermediate time window less explored. Here we reveal a metastable state with broken glide-plane symmetry in photo-doped Ca2RuO4 using time-resolved optical second-harmonic generation and birefringence measurements. We find that the metastable state appears long after intralayer antiferromagnetic order has melted and photo-carriers have recombined. Its properties are distinct from all known states in the equilibrium phase diagram and are consistent with intralayer ferromagnetic order. Furthermore, model Hamiltonian calculations reveal that a non-thermal trajectory to this state can be accessed via photo-doping. Our results expand the search space for out-of-equilibrium electronic matter to metastable states emerging at intermediate timescales.
DOI: 10.1038/s41567-024-02752-1
Source: https://www.nature.com/articles/s41567-024-02752-1