Dirac and Heavy Fermions in CeCoAs2 and CeAgAs2 and Their Sensitivity to Uniaxial Strain

Ternary Sb square-net compounds RTSb2 (where R=La, Ce and T =Cu, Ag, Au) have recently attracted interest due to observation of anisotropic Dirac fermions, charge density wave (CDW), and superconductivity, serving as a new playground for studying these intertwined orders. Electronic properties are dominated by the Dirac-like bands, originating from Sb square nets, that form the Fermi surface with nested segments, susceptible to CDW. In Ce-based compounds, these itinerant bands hybridize with the local moments in the Ce 4f states, leading to Kondo screening and heavy fermions. As-based materials, LaAgAs2 and CeAgAs2were expected to behave very similarly, now with As forming the square net. However, the crystal structure analysis revealed that within the As planes, As atoms form cis-trans chains instead of square-net, leading to orthorhombicity of <0.1%.  This should have a profound consequence on the electronic structure and provide an easy tuning knob by a uniaxial strain.

三元锑方格网（square-net）化合物RTSb₂（其中R为La、Ce，T为Cu、Ag、Au）近来备受学界关注，因其被观测到存在各向异性狄拉克费米子（anisotropic Dirac fermions）、电荷密度波（charge density wave, CDW）与超导性，成为研究这类相互交织有序态的全新研究平台。该类材料的电子性质由源自锑方格网的类狄拉克能带主导，这类能带形成了带有嵌套段的费米面，易于触发电荷密度波相变。在铈基化合物中，这类巡游能带与铈4f轨道态中的局域磁矩发生杂化，进而引发近藤屏蔽（Kondo screening）与重费米子（heavy fermions）效应。对于含砷材料LaAgAs₂与CeAgAs₂，此前学界普遍预期其表现会与前述锑方格网化合物极为相似——此时由砷原子构成方格网结构。然而晶体结构分析表明，在砷原子平面内，砷原子实际形成的是顺反链而非方格网，导致材料产生小于0.1%的正交畸变（orthorhombicity）。这一结构特征将对材料的电子结构产生深远影响，并为通过单轴应变（uniaxial strain）实现便捷调控提供了可行的调控旋钮。

搜集汇总

背景与挑战

背景概述

该数据集聚焦于CeCoAs2和CeAgAs2化合物，研究其电子结构中的狄拉克费米子和重费米子特性。这些材料表现出电荷密度波和超导性等交织序，其中As原子形成顺-反链而非方网结构，导致轻微正交畸变，从而影响电子行为。数据集特别关注单轴应变作为调控这些电子性质的敏感参数，为理解材料中的量子现象提供了实验基础。