近日，美国伊利诺伊大学香槟分校的Vidya Madhavan及其研究团队取得一项新进展。经过不懈努力，他们实现RbV₃Sb₅中电荷密度波态的光学操纵。相关研究成果已于2024年6月12日在国际权威学术期刊《自然》上发表。

本文利用激光耦合扫描隧道显微镜对RbV₃Sb₅进行了深入研究。通过沿高对称方向施加线偏振光，研究人员观察到CDW（电荷密度波）峰的相对强度可实现可逆的开关变化，这一发现揭示了显著的电伸缩响应，并指向了强烈的非线性电子-声子耦合。此外，在垂直磁场中也观察到了类似的CDW强度开关现象，这揭示了不寻常的压磁响应，并且这一现象需要时间反演对称性破缺。

研究团队证实，满足这些约束条件的最简单的CDW是由键电荷序和环路电流的非相组合构成的，他们将其命名为同成分CDW磁相。这一研究的激光扫描隧穿显微镜数据，为相关材料中复杂量子现象的动态光学控制提供了新的可能性。

据悉，在没有自旋序的情况下，时间反演对称性的破缺表明存在不寻常的相位，如轨道磁性和环路电流。最近发现的笼目超导体RbV₃Sb₅(其中A为K, Rb或Cs)显示出奇异的电荷密度波(CDW)状态，并且已经成为容纳环路电流相的材料的强有力候选。然而，由于相互矛盾的实验数据，CDW破缺时间反演对称性的观点正受到激烈的争论。

附：英文原文

Title: Optical manipulation of the charge-density-wave state in RbV₃Sb₅

Author: Xing, Yuqing, Bae, Seokjin, Ritz, Ethan, Yang, Fan, Birol, Turan, Capa Salinas, Andrea N., Ortiz, Brenden R., Wilson, Stephen D., Wang, Ziqiang, Fernandes, Rafael M., Madhavan, Vidya

Issue&Volume: 2024-06-12

Abstract: Broken time-reversal symmetry in the absence of spin order indicates the presence of unusual phases such as orbital magnetism and loop currents. The recently discovered kagome superconductors AV₃Sb₅ (where A is K, Rb or Cs) display an exotic charge-density-wave (CDW) state and have emerged as a strong candidate for materials hosting a loop current phase. The idea that the CDW breaks time-reversal symmetry is, however, being intensely debated due to conflicting experimental data. Here we use laser-coupled scanning tunnelling microscopy to study RbV₃Sb₅. By applying linearly polarized light along high-symmetry directions, we show that the relative intensities of the CDW peaks can be reversibly switched, implying a substantial electro-striction response, indicative of strong nonlinear electron–phonon coupling. A similar CDW intensity switching is observed with perpendicular magnetic fields, which implies an unusual piezo-magnetic response that, in turn, requires time-reversal symmetry breaking. We show that the simplest CDW that satisfies these constraints is an out-of-phase combination of bond charge order and loop currents that we dub a congruent CDW flux phase. Our laser scanning tunnelling microscopy data open the door to the possibility of dynamic optical control of complex quantum phenomenon in correlated materials.

DOI: 10.1038/s41586-024-07519-5

Source: https://www.nature.com/articles/s41586-024-07519-5