AI 中文总结
该研究构建了与均匀晶格形变耦合的公度电荷密度波的朗道理论，解释了NbS₃链的CDW相关观测，提出振幅-应变自由能，为锁相理论和密度波应变调控实验提供新视角。
AI 中文摘要
我们构建了针对电荷密度波（CDW）的最小朗道理论，该CDW的公度性相对于形变晶格定义。研究动机来自对孤立单链NbS₃的近期观测，其表现出公度CDW态，伴随晶格常数收缩6%。均匀拉伸a₀→a₀(1+ε)会将倒格波矢变为G(ε)=G₀/(1+ε)，因此N重公度CDW的波矢为Q_C(ε)=G(ε)/N，而非公度不稳定性偏好的波矢Q_IC保持固定。我们针对N=3和N=4提出了振幅-应变自由能，其中CDW通过缓解Q_C(ε)与Q_IC的失配诱导有限均匀应变。失配由CDW与晶格按其刚度比分担；由于CDW刚度随CDW振幅增长，随CDW发展，晶格承担的失配份额逐渐增加。我们的结果表明需重新审视锁相理论及密度波系统的应变调控实验。
英文摘要
We formulate a minimal Landau theory for a charge-density wave (CDW) whose commensurability is defined with respect to a deformed lattice. The motivation is provided by recent observations on an isolated single NbS$_3$ chain, which exhibits a commensurate CDW state accompanied by a $6\%$ shrinkage of the lattice constant. A uniform stretch $a_0\to a_0(1+\varepsilon)$ changes the reciprocal lattice wave number to $G(\varepsilon)=G_0/(1+\varepsilon)$, so that an $N$-fold commensurate CDW has the wave number $Q_\mathrm{C}(\varepsilon)=G(\varepsilon)/N$, whereas the wave number $Q_\mathrm{IC}$ favored by the incommensurate instability remains fixed. We propose an amplitude-strain free energy for both $N=3$ and $N=4$, in which the CDW induces a finite uniform strain by relieving the mismatch between $Q_\mathrm{C}(\varepsilon)$ and $Q_\mathrm{IC}$. The mismatch is shared between the CDW and the lattice in a proportion set by their stiffness ratio; since the CDW stiffness grows with the CDW amplitude, the lattice takes up an increasing share of the mismatch as the CDW develops. Our results suggest a reexamination of lock-in theories and of strain-tuning experiments on density-wave systems.
