Most metallic transition metal dichalcogenides undergo charge density wave (CDW) instabilities with similar or identical ordering vectors in bulk and in single layer, albeit with different critical temperatures. Metallic 1 T-TiTe 2 is a remarkable exception as it shows no evidence of charge density wave formation in bulk, but it displays a stable 2 × 2 reconstruction in single-layer form. The mechanism for this 3D-2D crossover of the transition is still unclear, although strain from the substrate and the exchange interaction have been pointed out as possible formation mechanisms. Here, by performing non-perturbative anharmonic calculations with gradient corrected and hybrid functionals, we explain the thickness behaviour of the transition in 1 T-TiTe. We demonstrate that the CDW in single-layer TiTe 2 occurs from the interplay of non-perturbative anharmonicity and an exchange enhancement of the electron-phonon interaction, larger in the single layer than in t...

中文翻译：

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1 T-TiTe 2中电荷密度波跃迁的厚度依赖性理论

尽管具有不同的临界温度，但大多数金属过渡金属二卤化物会经历电荷密度波（CDW）的不稳定性，它们具有相似或相同的有序排列的整批和单层有序向量。金属1 T-TiTe 2是一个显着的例外，因为它没有显示出大量形成电荷密度波的迹象，但以单层形式显示了稳定的2×2重构。尽管已经指出了来自底物的应变和交换相互作用是可能的形成机理，但这种3D-2D过渡转变的机理仍不清楚。在这里，通过执行具有梯度校正和混合函数的非微扰非谐计算，我们解释了1 T-TiTe中跃迁的厚度行为。