Charge density wave (CDW) ordering has been an important topic of study for a long time owing to its connection with other exotic phases such as superconductivity and magnetism. The RTe3 (R = rare-earth elements) family of materials provides a fertile ground to study the dynamics of CDW in van der Waals layered materials, and the presence of magnetism in these materials allows to explore the interplay among CDW and long range magnetic ordering. Here, we have carried out a high-resolution angle-resolved photoemission spectroscopy (ARPES) study of a CDW material GdTe3, which is antiferromagnetic below 12 K, along with thermodynamic, electrical transport, magnetic, and Raman measurements. Our Raman spectroscopy measurements show the presence of CDW amplitude mode at room temperature, which remains prominent when the sample is thinned down to 4-layers by exfoliation. Our ARPES data show a two-fold symmetric Fermi surface with both gapped and ungapped regions indicative of the partial nesting. The gap is momentum dependent, maximum along G-Z and gradually decreases going towards G - M. Our study provides a platform to study the dynamics of CDW and its interaction with other physical orders in two- and three-dimensions.
Microwave-to-optical transduction using magnon-exciton coupling in a layered antiferromagnet
City College of New York（纽约市立学院）；Graduate Center of the City University of New York (CUNY)（纽约市立大学研究生中心）；CUNY Advanced Science Research Center（纽约市立大学高级科学研究中心）；University of Chemistry and Technology Prague（布拉格化工大学）；Columbia University（哥伦比亚大学）；University of Chicago（芝加哥大学）；Rheinland-Pfälzische Technische Universität（莱茵兰-普法尔茨科技大学）
Intrinsic magnetic topological insulators in van der Waals layered MnBi$_2$Te$_4$-family materials
磁性与拓扑学的相互作用是凝聚态物理和材料科学的重要研究课题，它为探索量子反常霍尔效应、轴子电动力学和马约拉纳费米子等新兴物理提供了巨大的机会。然而，由于缺乏合适的工作材料，这些奇异的物理效应在实验中很少实现。在这里，我们预测，范德华层状MnBi $_2$ Te $_4$ -家庭材料显示二维（2D）铁磁性在单层和三维（3D）$A$型反铁磁性在块体，这可以作为一个新一代的材料平台，为国家的最先进的研究。值得注意的是，我们预测非常丰富的拓扑量子效应与突出的功能，在实验可用的材料MnBi $_2$ Te $_4$，包括3D反铁磁拓扑绝缘体与长期寻求的拓扑轴子状态，II型磁性Weyl半金属（WSM）与简单的一对Weyl点，和高温本征QAH效应。这些惊人的预测，如果实验证明，可能会深刻地改变拓扑量子物理学的未来研究和技术。
Intermittent dynamics of antiferromagnetic phase in inhomogeneous iron-based chalcogenide superconductor
以不同电子自由度为特征的相共存通常发生在层状超导体中。其中，碱性插层硫族化合物是顺磁（PAR）和反铁磁（AFM）相共存的模型系统，但不同阶段的时间行为仍然是未知的。在这里，我们报告的第一个可视化的原子运动在颗粒相的K $_{x}$ Fe $_{2-y}$ Se $_2$使用X射线光子相关光谱。与PAR相不同，AFM纹理揭示了间歇性的动态与雪崩在马氏体。当冷却到超导转变温度T $_c$时，AFM相经历了一个反常的慢化行为，表明AFM相中原子的运动与超导性之间存在直接关系。除了为层状超导体中类似雪崩的动力学提供令人信服的证据外，这些结果还为描述非均匀固体中量子态的新理论模型提供了基础。
