We use total scattering to study the reversible transition between the polar $1T^{\prime }$ and nonpolar $T_d$ phases of layered $\mathrm{Mo}{\mathrm{Te}}_2$ taking place at 240 K. Whereas, macroscopically, the transition appears to be first order, locally, it is not. In particular, a great deal of the stacking sequence of Te-Mo-Te layers characteristic of the polar $1T^{\prime }$ phase persists locally in the nonpolar $T_d$ phase, and vice versa, over a broad temperature range extending about 100 K both below and above the transition. The intermixing ratio for the two sequences evolves gradually across the transition temperature, consistent with a second-order transition behavior. The presence of coexisting local polar and nonpolar regions and the resulting variety of internal interfaces where the spatial inversion symmetry is broken may be behind some of the unusual electronic properties of $T_d\text{−}\mathrm{Mo}{\mathrm{Te}}_2$, including its putative type-II Weyl semimetal state.

中文翻译：

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MoTe2极性和非极性相中的局部结构记忆效应

我们使用总散射来研究极地之间的可逆转变 $\mathrm{1个}{Ť}^{\prime }$ 和非极性 ${Ť}_d$ 分层的阶段 $莫{特}_{\mathrm{2个}}$发生在240K。从宏观上看，过渡似乎是一阶的，局部而言不是。尤其是极地特有的Te-Mo-Te层的堆叠顺序$\mathrm{1个}{Ť}^{\prime }$ 相在非极性中局部存在 ${Ť}_d$反之亦然，反之亦然，在过渡温度之上和之下延伸约100 K的宽温度范围内。这两个序列的混合比在过渡温度范围内逐渐演化，与二阶过渡行为一致。共存的局部极性和非极性区域的存在，以及由此导致的各种内部界面（其中空间反转对称性被破坏）可能是由于某些非常规电子性质所致。${Ť}_d\text{-}莫{特}_{\mathrm{2个}}$，包括其推定的II型Weyl半金属态。