Roy Aditya Prasad, Bajaj Naini, Mittal Ranjan, Babu Peram D, Bansal Dipanshu
Department of Mechanical Engineering, Indian Institute of Technology Bombay, Mumbai, MH 400076, India.
Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai, MH 400085, India.
Phys Rev Lett. 2021 Mar 5;126(9):096401. doi: 10.1103/PhysRevLett.126.096401.
The topology of the Fermi surface controls the electronic response of a metal, including charge density wave (CDW) formation. A topology conducive for Fermi surface nesting (FSN) allows the electronic susceptibility χ_{0} to diverge and induce a CDW at wave vector q_{CDW}. Kohn extended the implications of FSN to show that the imaginary part of the lattice dynamical susceptibility χ_{L}^{''} also responds anomalously for all phonon branches at q_{CDW}-a phenomenon referred to as the Kohn anomaly. However, materials exhibiting multiple Kohn anomalies remain rare. Using first-principles simulations of χ_{0} and χ_{L}^{''}, and previous scattering measurements [Crummett et al., Phys. Rev. B 19, 6028 234 (1979)PRBMDO0163-1829], we show that α-uranium harbors multiple Kohn anomalies enabled by the combined effect of FSN and "hidden" nesting, i.e., nesting of electronic states above and below the Fermi surface. FSN and hidden nesting lead to a ridgelike feature in the real part of χ_{0}, allowing interatomic forces to modulate strongly and multiple Kohn anomalies to emerge. These results emphasize the importance of hidden nesting in controlling χ_{0} and χ_{L}^{''} to exploit electronic and lattice states and enable engineering of advanced materials, including topological Weyl semimetals and superconductors.
费米面的拓扑结构控制着金属的电子响应，包括电荷密度波（CDW）的形成。有利于费米面嵌套（FSN）的拓扑结构会使电子磁化率χ₀发散，并在波矢q₍CDW₎处诱导出CDW。科恩扩展了FSN的影响，表明晶格动力学磁化率χₗ⁽⁾的虚部在q₍CDW₎处对所有声子分支也有异常响应——这一现象被称为科恩反常。然而，表现出多个科恩反常的材料仍然很少见。通过对χ₀和χₗ⁽⁾进行第一性原理模拟，以及之前的散射测量[克鲁梅特等人，《物理评论B》19，6028 234（1979）PRBMDO0163 - 1829]，我们表明α - 铀具有多个科恩反常，这是由FSN和“隐藏”嵌套（即费米面上下电子态的嵌套）的综合效应导致的。FSN和隐藏嵌套在χ₀的实部产生了类似脊状的特征，使得原子间力能够强烈调制，并出现多个科恩反常。这些结果强调了隐藏嵌套在控制χ₀和χₗ⁽⁾以利用电子态和晶格态以及实现包括拓扑外尔半金属和超导体在内的先进材料工程方面的重要性。
