三元锑化物La$T$Sb$_2$ ($T$ = Cu, Ag)的磁输运与电子结构研究
Magneto-transport and electronic structure studies of ternary antimonides, La$T$Sb$_2$ ($T$ = Cu, Ag)
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中文总结 AI 辅助
本研究通过磁输运和光电子能谱结合DFT计算，发现La$T$Sb$_2$ ($T$ = Cu, Ag)中仅Ag化合物呈现CDW现象，且Sb方形网格与其形成相关，为理解CDW机制提供了光谱基准。
中文摘要 AI 辅助
我们利用磁输运和光电子能谱研究，并结合基于密度泛函理论（DFT）的从头计算，研究了基于Sb方形网格的狄拉克半金属三元锑化物La$T$Sb$_2$ ($T$ = Cu, Ag)。我们的结果表明，这两种化合物都表现出正的电阻温度系数、线性磁阻（MR），以及在低温（2-30 K）下偏离费米液体行为。但只有$T$ = Ag的化合物表现出电荷密度波（CDW）现象的特征，其温度依赖的MR数据结果表明，单带半经典输运不足以理解其输运行为。$\text{DFT}+U$研究表明，在两种样品中，在存在自旋-轨道耦合（SOC）的情况下，对Cu 3$d$和Ag 4$d$电子的在位库仑相互作用（$U$）是重现实验价带谱所必需的。Sb 3$d$、4$d$芯能级谱结合$\text{DFT}+U$计算和La 3$d$谱证实了两种样品中不等价Sb位点的存在及其影响。与$T$ = Cu化合物遵循预期的温度依赖性芯能级锐化不同，$T$ = Ag化合物在CDW相中表现出异常的低温展宽。Sb 3$d$谱的分析表明，Sb方形网格与$T$ = Ag化合物中的CDW现象有关。对$T$ = Ag的温度依赖性紫外光电子能谱研究表明，在低于CDW转变温度的温度下，$\epsilon_F$处的谱态密度略有下降。这些芯能级研究为比较CDW和非CDW系统以及阐明局部电子环境在CDW形成中的作用提供了宝贵的光谱基准。
英文摘要
We investigate Sb square net-based Dirac semimetallic ternary antimonides La$T$Sb$_2$ ($T$ = Cu, Ag) using magnetotransport and photoelectron spectroscopic studies, complemented by density functional theory (DFT) based ab initio calculations. Our results show that both compounds exhibit a positive temperature coefficient of resistivity, linear magnetoresistance (MR), and a deviation from Fermi liquid behaviour at low temperatures (2-30 K). But only $T$ = Ag compound exhibit signature of charge density wave (CDW) phenomena and the results of its temperature dependent MR data suggest that single-band semiclassical transport is not sufficient to understand the transport behaviour. $\text{DFT}+U$ studies show that in both samples, an on-site Coulomb interaction ($U$) for Cu 3$d$ and Ag 4$d$ electrons, in the presence of spin-orbit coupling (SOC) is required to reproduce experimental valence band spectra. Sb 3$d$, 4$d$ core-level spectra combined with $\text{DFT}+U$ calculations and La 3$d$ spectra confirm the presence and effects of inequivalent Sb sites for both the samples. In contrast to the $T$ = Cu compound, which follows expected temperature-dependent core-level sharpening, the $T$ = Ag compound exhibits an anomalous low-temperature broadening in the CDW phase. The analysis of Sb 3$d$ spectra suggests Sb square nets are linked to CDW phenomena in the $T$ = Ag compound. Temperature-dependent ultraviolet photoemission spectroscopic studies on $T$ = Ag show a small decrement in spectral DOS at the $ε_F$ for the temperature below the CDW transition temperature. These core-level studies provide a valuable spectroscopic benchmark for comparing CDW and non-CDW systems and clarifying the role of local electronic environments in CDW formation.
发表机构
- Indian Institute of Technology Mandi（印度技术学院曼迪分校）
- Indian Institute of Science Education and Research, Bhopal（印度科学教育研究学院博帕尔分校）
- Tata Institute of Fundamental Research（塔塔基础研究所）
- Okinawa Institute of Science and Technology (OIST) Graduate University（冲绳科学技术大学院大学）
- Toyota Technological Institute（名古屋工业大学）
- Japan Science and Technology Agency（日本科学技术振兴机构）
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