[论文解读] Atypical sliding and Moire ferroelectricity in pure multilayer graphene

Liu Yang, Shi-Ping Ding+2 more|PubMed|May 12, 2023

Graphene research and applications被引用 8

一句话总结

论文通过第一性原理提供证据：多层石墨烯超过三层在层间滑动下可以具备铁电性，极性态源于跨层堆叠对称性破缺和非常规的Moire铁电模式。

ABSTRACT

Most nonferroelectric two-dimensional materials can be endowed with so-called sliding ferroelectricity via nonequivalent homobilayer stacking, which is not applicable to monoelement systems like pure graphene bilayer with inversion symmetry at any sliding vector. Herein, we show first-principles evidence that multilayer graphene with N>3 can all be ferroelectric, where the polarizations of polar states stem from the symmetry breaking in stacking configurations of across layer instead of adjacent layer, which are electrically switchable via interlayer sliding. The nonpolar states can also be electrically driven to polar states via sliding, and more diverse states with distinct polarizations will emerge in more layers. In contrast to the ferroelectric moiré domains with opposite polarization directions in twisted bilayers reported previously, the moiré pattern in some multilayer graphene systems (e.g., twisted monolayer-trilayer graphene) possess nonzero net polarizations with domains of the same direction separated by nonpolar regions, which can be electrically reversed upon interlayer sliding. The distinct moiré bands of two polar states should facilitate electrical detection of such sliding moiré ferroelectricity during switching.

研究动机与目标

• 激发在纯多层石墨烯（超越双层）中寻找铁电性的兴趣。
• 展示极性态来自跨层堆叠对称性破缺，而非相邻层对称性。
• 通过层间滑动演示极性态的电可切换性。
• 强调非极性态通过滑动可被驱动变为极性态，且能量几乎简并。
• 探讨层数增加至N>3如何扩大潜在的极性配置数量。

提出的方法

• 进行第一性原理计算，研究多层石墨烯中的堆叠配置及其极性。
• 识别源自跨层堆叠对称性破缺的极性态。
• 评估层间滑动作为在极性态与非极性态之间实现电致切换的机制。
• 比较扭曲多层石墨烯系统中的Moire模式及净极化。
• 表征不同的Moire带如何与极性态切换及电学可检测性相关联。

实验结果

研究问题

• RQ1 纯多层石墨烯（N>3）在某些配置下是否仍具有反演对称性的情况下也能表现出铁电性？
• RQ2 极性态是否由跨层堆叠对称性破缺稳定并可通过层间滑动切换？
• RQ3 扭曲的多层石墨烯系统中的Moire模式是否产生可通过电控制的净极化？
• RQ4 随着层数增加N，极性配置及其能量的多样性如何变化？

主要发现

• 根据第一性原理证据，多层石墨烯在N>3时可以是铁电的。
• 极性态源自跨层对称性破缺，而不仅仅是相邻层的对称性。
• 非极性态可以通过层间滑动被驱动变为极性态，且能量几乎简并。
• 某些Moire模式（例如扭转单层-三层石墨烯）具有非零净极化，同向域被非极性区域分隔。
• 与极性态对应的不同Moire带使在切换时能够实现电学检测。