论文标题
bani $ _2 $ a $ _2 $的声子软化和减慢电荷密度波动的变化
Phonon softening and slowing down of charge-density-wave fluctuations in BaNi$_2$As$_2$
论文作者
论文摘要
bani $ _2 $ as $ _2 $是铁pnictide超导体的非磁性类似物，在其四方状态下表现出不合格的电荷密度 - 波（IC-CDW）和相当大的弹性抗性。在这项工作中，使用高分辨率的弹性X射线散射研究了BANI $ _2 $ AS $ _2 $与IC-CDW和平面内晶格失真相关的$ _2 $。平面横向声音子声子在温度下没有弹性升高，在弹性强烈增加的温度下没有软化，这表明后者是电子驱动的。系统的声子测量结果揭示了IC-CDW在冷却后分为两个阶段发生的：首先阻尼的声子首先软化到零能量，远高于IC-CDW排序温度，然后产生的准级别IC-CDW波动逐渐减慢并凝聚到静态IC-CDW阶。我们观察结果的可能起源是四方bani $ _2 $ as $ _2 $是单轴的IC-CDW，它提供了有利于无序IC-CDW调制的额外自由度，并通过弱耦合到晶格来解释弹性。
BaNi$_2$As$_2$ is a nonmagnetic analogue of the iron pnictide superconductors, and in its tetragonal state exhibits an incommensurate charge-density-wave (IC-CDW) and a sizable elastoresistance. In this work, phonons in BaNi$_2$As$_2$ associated with the IC-CDW and uniform in-plane lattice distortions are investigated using high-resolution inelastic X-ray scattering. The in-plane transverse acoustic phonons reveal no softening at temperatures where the elastoresistance increases strongly, indicating the latter to be electronically driven. Systematic phonon measurements reveal the IC-CDW occurs in two stages upon cooling: underdamped phonons first soften to zero energy well above the IC-CDW ordering temperature, then the resulting quasielastic IC-CDW fluctuations gradually slow down and coalesce into the static IC-CDW order. A possible origin for our observations is the IC-CDW in tetragonal BaNi$_2$As$_2$ being uniaxial, which provides an additional Ising degree of freedom favorable for disordered IC-CDW modulations, and accounts for the elastoresistance through a weak coupling to the lattice.
