Martin Gutierrez-Amigo, Ðorđe Dangić, Chunyu Guo, Claudia Felser, Philip J. W. Moll, Maia G. Vergniory, Ion Errea
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引用次数: 0
摘要
自四年前发现 AV3Sb5 卡戈米金属家族以来,其电荷密度波(CDW)机制和由此产生的结构一直是一个令人费解的难题。事实上,对电荷密度波的起源和结构缺乏共识阻碍了人们对这一新现象的理解。在这里,我们利用第一原理计算中的非微扰处理非谐波性,揭示了 CsV3Sb5 中的电荷密度转变是由材料的大电子-声子耦合驱动的,而 CDW 状态的熔化则归因于离子熵和晶格非谐波性。计算得出的转变温度与实验结果非常吻合,这意味着软模式物理是电荷密度波转变的核心。与纯卡格姆晶格的标准假设相反,电荷密度波本质上是三维的,因为它是由 L 点的不稳定声子引发的。由于 M 点没有声子的参与,我们得以将由此产生的对称性限制在六个可能的空间群内。软模式异常巨大的电子-声子线宽解释了为什么非弹性散射实验没有观察到任何软化声子。我们预见到大的非谐波效应无处不在,而且可能是理解其他神户系中所观察到的现象的基础。AV3Sb5 kagome 金属中的电荷密度波态与几种非常规和有趣的现象密切相关,但其起源和结构仍存在争议。在这里,非微扰计算表明电子-声子耦合是驱动机制,电荷密度波态的熔化归因于离子熵和晶格非谐性。
Phonon collapse and anharmonic melting of the 3D charge-density wave in kagome metals
The charge-density wave (CDW) mechanism and resulting structure of the AV3Sb5 family of kagome metals has posed a puzzling challenge since their discovery four years ago. In fact, the lack of consensus on the origin and structure of the CDW hinders the understanding of the emerging phenomena. Here, by employing a non-perturbative treatment of anharmonicity from first-principles calculations, we reveal that the charge-density transition in CsV3Sb5 is driven by the large electron-phonon coupling of the material and that the melting of the CDW state is attributed to ionic entropy and lattice anharmonicity. The calculated transition temperature is in very good agreement with experiments, implying that soft mode physics are at the core of the charge-density wave transition. Contrary to the standard assumption associated with a pure kagome lattice, the CDW is essentially three-dimensional as it is triggered by an unstable phonon at the L point. The absence of involvement of phonons at the M point enables us to constrain the resulting symmetries to six possible space groups. The unusually large electron-phonon linewidth of the soft mode explains why inelastic scattering experiments did not observe any softened phonon. We foresee that large anharmonic effects are ubiquitous and could be fundamental to understand the observed phenomena also in other kagome families. The charge-density wave state in AV3Sb5 kagome metals is intimately related to several unconventional and intriguing phenomena, but its origin and structure are still under debate. Here, non-perturbative calculations indicate a large electron-phonon coupling as the driving mechanism, attributing the melting of the charge-density wave state to ionic entropy and lattice anharmonicity.
期刊介绍:
Communications Materials, a selective open access journal within Nature Portfolio, is dedicated to publishing top-tier research, reviews, and commentary across all facets of materials science. The journal showcases significant advancements in specialized research areas, encompassing both fundamental and applied studies. Serving as an open access option for materials sciences, Communications Materials applies less stringent criteria for impact and significance compared to Nature-branded journals, including Nature Communications.