Impact of Sb degrees of freedom on the charge density wave phase diagram of the kagome metal CsV3Sb5
Impact of Sb degrees of freedom on the charge density wave phase diagram of the kagome metal CsV3Sb5
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DOI：
10.1103/physrevb.107.205131
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发表时间：
2022-12
影响因子：
3.7
通讯作者：
E. Ritz;R. Fernandes;T. Birol
中科院分区：
文献类型：
--
作者：
E. Ritz;R. Fernandes;T. Birol
阐明引起AV$_3$Sb$_5$（A=Cs，K，Rb）族可果美金属的电荷密度波（CDW）不稳定性的微观机制对于理解它们的独特性质（包括超导性）至关重要。在这些化合物中，在$M$和$L$点处具有波矢量的不同CDW相在能量上是有利的，从而打开了通过适当的外部参数来调谐CDW阶的类型的可能性。在这里，我们揭示了CDW景观CsV$_3$Sb$_5$通过第一性原理计算和现象学的结合，其中包括提取系数的CDW朗道自由能膨胀密度泛函理论。我们发现，虽然在交错的三六角形CDW相的kagome晶格的主要结构扭曲是沿着最近邻的V-V键，与Sb离子相关的扭曲在这个和所有其他CDW状态的能量增益中起着决定性的作用。此外，从不同的晶胞离子位移之间的耦合是小的，从而解释了存在多个CDW不稳定性与不同的调制沿着c轴。我们还研究了压力和温度如何影响CsV$_3$Sb$_5$的CDW相。增加压力并没有改变交错的三六边形CDW基态，即使$M$点CDW不稳定性消失之前的$L$点，一个行为，我们归因于大的非线性之间的耦合序参数。在改变温度时，我们发现一个狭窄的制度，其中另一个过渡可以发生，朝着一个三六角形的大卫星CDW相。我们讨论了我们的研究结果的影响，通过比较它们与实验对这种化合物。
Elucidating the microscopic mechanisms responsible for the charge density wave (CDW) instability of the AV$_3$Sb$_5$ (A=Cs, K, Rb) family of kagome metals is critical for understanding their unique properties, including superconductivity. In these compounds, distinct CDW phases with wave-vectors at the $M$ and $L$ points are energetically favorable, opening the possibility of tuning the type of CDW order by appropriate external parameters. Here, we shed light on the CDW landscape of CsV$_3$Sb$_5$ via a combination of first-principles calculations and phenomenology, which consists of extracting the coefficients of the CDW Landau free-energy expansion from density functional theory. We find that while the main structural distortions of the kagome lattice in the staggered tri-hexagonal CDW phase are along the nearest-neighbor V-V bonds, distortions associated with the Sb ions play a defining role in the energy gain in this and all other CDW states. Moreover, the coupling between ionic displacements from different unit cells is small, thus explaining the existence of multiple CDW instabilities with different modulations along the c-axis. We also investigate how pressure and temperature impact the CDW phase of CsV$_3$Sb$_5$. Increasing pressure does not change the staggered tri-hexagonal CDW ground state, even though the $M$-point CDW instability disappears before the $L$-point one, a behavior that we attribute to the large nonlinear coupling between the order parameters. Upon changing the temperature, we find a narrow regime in which another transition can take place, toward a tri-hexagonal Star-of-David CDW phase. We discuss the implications of our results by comparing them with experiments on this compound.