论文标题
NMR证据证明PEIERLS过渡中的分层正方网络化合物LAAGSB $ _2 $
NMR evidence for a Peierls transition in the layered square-net compound LaAgSb$_2$
论文作者
论文摘要
我们测量了中央（$ 1/2 \ leftrightArrow -1/2 $）和第一颗卫星（$ \ pm3/2 \ leftrightArrow \ pm1/2 $）\ la \ nmr Spectra的线条作为LaagsB $ _2 $中温度的函数，以阐明Attition and Transition Attition and Trandition Attition and Trandition and Tartinition（CD）。 $ t_ \ text {cdw1} = 207 $ k和$ t_ \ text {cdw2} = 186 $ k。在正常状态下，骑士移位k揭示了与温度降低相当线性的关系，这与降低的温度相当线性关系，这归因于旋转兴奋谱中的pseudoGap，指向材料的材料，指向不一致的金属。进一步冷却后，K更陡峭地下降到$ t_ \ text {cdw1} $以下，这表明pseudoGap顶部的部分费米表面差距开口。在我们的研究中，最引人注目的发现是以$ t_ \ text {cdw1} $对$ h \ parallel c $观察到的卫星线的明确分裂，其温度依赖性作为弱耦合限制的BCS订单参数的行为，表明CDW过渡会导致周期性的lattice扭曲。因此，我们的NMR调查结果表明，LAAGSB $ _2 $中的CDW过渡是PEIERLS类型，这是由Fermi级别附近的电子不稳定驱动的。
We measured the central ($1/2\leftrightarrow -1/2$) and first satellite ($\pm3/2\leftrightarrow \pm1/2$) lines of the \la\ NMR spectra as a function of temperature in LaAgSb$_2$, in order to elucidate the origin and nature of the charge-density-wave (CDW) transitions at $T_\text{CDW1}=207$ K and $T_\text{CDW2}=186$ K. In the normal state, the Knight shift K reveals a fairly linear relationship with decreasing temperature, which is ascribed to a pseudogap in the spin excitation spectrum, pointing towards the material being an unconventional metal. Upon further cooling, K decreases more steeply below $T_\text{CDW1}$, indicative of the partial Fermi surface gap opening on top of the pseudogap. The most remarkable finding in our study is a clear splitting of the satellite lines at $T_\text{CDW1}$ observed for $H\parallel c$, whose temperature dependence behaves as the BCS order parameter in the weak-coupling limit, evidencing that the CDW transition induces the periodic lattice distortion. Our NMR findings therefore demonstrate that the CDW transition in LaAgSb$_2$ is of Peierls type, being driven by the electronic instability in the vicinity of the Fermi level.
