发表机构
Stockholm University; Uppsala University; Technion–Israel Institute of Technology; KTH Royal Institute of Technology; Australian National University（斯德哥尔摩大学; 乌普萨拉大学; 以色列理工学院; 瑞典皇家理工学院; 澳大利亚国立大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究利用超快三维电子衍射解析二氧化钒光致绝缘体-金属转变中的原子轨迹，揭示V-V二聚化驱动能隙坍缩的线性路径，将时间分辨衍射发展为瞬态晶体学。
AI 中文摘要
关联材料中的超快相变通常通过选定的衍射峰强度或衍射峰位移来推断，这使得潜在的三维原子轨迹难以捉摸。解析这些轨迹对于识别哪些原子运动驱动电子性质的变化以及它们如何与电子自由度耦合至关重要。我们在二氧化钒（VO2）中应对这一挑战，这是一种关联氧化物，其绝缘单斜（M1）相与金属金红石（R）相之间存在接近室温的转变。为此，我们引入了超快三维电子衍射技术，该技术能够精修瞬态晶胞以及内部V和O坐标，从而揭示相变过程中的V-V二聚化和锯齿运动。精修后的原子坐标在相变期间沿实空间中的线性轨迹演化，这与早期工作中通过更间接的观测推断出的非线性或顺序转变路径形成对比。将每个V-V对视为关联单元的量子多体计算表明，二聚化产生了导致电子能隙的能级分裂，而配对V原子之间的非局域电子相互作用进一步增强了这一效应。当二聚化消失时，能隙坍缩。这项工作将时间分辨衍射从序参量追踪转变为瞬态晶体学，直接将原子轨迹与关联材料中的电子机制联系起来。
英文摘要
Ultrafast phase transitions in correlated materials are often inferred from selected diffraction peak intensities or diffraction peak displacements, leaving the underlying three-dimensional atomic trajectories elusive. Resolving these trajectories is essential for identifying which atomic motions drive changes in electronic properties and how they couple to electronic degrees of freedom. We address this challenge in vanadium dioxide (VO2), a correlated oxide with a near-room-temperature transition between the insulating monoclinic (M1) phase and metallic rutile (R) phase. For this purpose, we introduce ultrafast three-dimensional electron diffraction, which enables refinement of the transient unit cell and internal V and O coordinates, revealing the V-V dimerization and zigzag motion during the phase transition. The refined atomic coordinates follow a linear trajectory in real space during the transition, in contrast to nonlinear or sequential transformation pathways inferred from more indirect observables in earlier work. Quantum many-body calculations treating each V-V pair as a correlated unit show that dimerization creates the level splitting responsible for the electronic gap, which is further enhanced by nonlocal electronic interactions between the paired V atoms. The gap collapses when dimerization is lost. This work turns time-resolved diffraction from order-parameter tracking into transient crystallography, directly connecting atomic trajectories to electronic mechanisms in correlated materials.
