该研究团队采用超快激光脉冲在Sr2IrO4中实现绝缘体-金属跃迁，并使用时间和角度分辨的光电发射光谱探测由此产生的动力学。研究人员观察到原本存在的能隙逐渐闭合，同时在能隙区域形成了弱重整化的电子能带。通过将这些观测结果与莫特能隙和哈伯德能带的理论预期，在温度和掺杂变化下的演化情况进行对比，研究人员明确否定了绝缘状态是由莫特相关性引起的假设。
相反，他们提出一个相关能带绝缘体图，其中反铁磁相关性在能隙打开中起关键作用。更广泛地说，这项研究结果表明，能量动量分解的非平衡动力学可以用来澄清相关材料中平衡状态的性质。
据悉，Sr2IrO4由于其结构和电子学与La2CuO4(高Tc 超导铜酸盐的母体化合物)相似而引起了人们的广泛关注。它被认为是一个强自旋轨道耦合的Jeff = 1/2 莫特绝缘子，但其绝缘基态的莫特性质尚未得到最终确定。
附：英文原文
Title: Light-induced insulator–metal transition in Sr2IrO4 reveals the nature of the insulating ground state
Author: Choi, Dongsung, Yue, Changming, Azoury, Doron, Porter, Zachary, Chen, Jiyu, Petocchi, Francesco, Baldini, Edoardo, Lv, Baiqing, Mogi, Masataka, Su, Yifan, Wilson, Stephen D., Eckstein, Martin, Werner, Philipp, Gedik, Nuh
Issue&Volume: 2024-7-8
Abstract: Sr2IrO4 has attracted considerable attention due to its structural and electronic similarities to La2CuO4, the parent compound of high-Tc superconducting cuprates. It was proposed as a strong spin–orbit-coupled Jeff = 1/2 Mott insulator, but the Mott nature of its insulating ground state has not been conclusively established. Here, we use ultrafast laser pulses to realize an insulator–metal transition in Sr2IrO4 and probe the resulting dynamics using time- and angle-resolved photoemission spectroscopy. We observe a gap closure and the formation of weakly renormalized electronic bands in the gap region. Comparing these observations to the expected temperature and doping evolution of Mott gaps and Hubbard bands provides clear evidence that the insulating state does not originate from Mott correlations. We instead propose a correlated band insulator picture, where antiferromagnetic correlations play a key role in the gap opening. More broadly, our results demonstrate that energy–momentum-resolved nonequilibrium dynamics can be used to clarify the nature of equilibrium states in correlated materials.
DOI: 10.1073/pnas.2323013121
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2323013121