AI 中文总结
研究人员通过第一性原理计算发现，Janus诱导的本征应变可调控单层NbSSiAs₂的电荷密度波相选择，结合外部应变还能实现电荷密度波序、拓扑与超导性的共存
AI 中文摘要
在二维材料中，控制竞争型电荷密度波（CDW）不稳定性之间的相选择仍具挑战性。本文的第一性原理计算表明，Janus诱导的本征拉伸应变将NbS₂的非M点软模倾向转向NbSSiAs₂的M点，从而选择出2×2型CDW重构。电声耦合分析显示，源于Nb的态与纵声学模之间的动量选择性耦合是M点不稳定性的起源。该重构相具有两种近简并的Nb三聚化构型，其相对稳定性可通过双轴应变调控。两种构型均保留了6-7 K量级的声子介导超导性，表明CDW序与超导性共存。压缩应变有利于1+3-中空构型，在保留超导性的同时诱导出带反转的Z₂非平庸态。综上，这些结果表明Janus诱导的本征应变是实现CDW相选择的内部结构途径，而外部应变可进入CDW序、拓扑与超导性共存的 regime
英文摘要
Controlling phase selection among competing charge-density-wave (CDW) instabilities remains challenging in two-dimensional materials. Here, first-principles calculations show that Janus-induced intrinsic tensile strain redirects the off-M soft-mode tendency of NbS$_2$ to the M point in NbSSiAs$_2$, selecting a $2\times2$ CDW reconstruction. Electron-phonon coupling analysis identifies momentum-selective coupling between Nb-derived states and a longitudinal acoustic mode as the origin of the M-point instability. The reconstructed phase hosts two nearly degenerate Nb-trimerized configurations whose relative stability is tuned by biaxial strain. Both configurations retain phonon-mediated superconductivity on the 6-7 K scale, indicating the coexistence of CDW order and superconductivity. Compressive strain favors the 1+3-hollow configuration and induces a band-inverted, $Z_2$-nontrivial state while preserving superconductivity. Together, these results identify Janus-induced intrinsic strain as an internal structural route for CDW phase selection, whereas external strain provides access to a regime in which CDW order, topology, and superconductivity coexist.
Comments13 pages,5 figures,1 table
