arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2108.10342cond-mat.mes-hallcond-mat.softcond-mat.str-el
收藏

无序莫尔超晶格中声子的退化

Degradation of phonons in disordered moiré superlattices

Héctor Ochoa, Rafael M. Fernandes

摘要:

莫尔超晶格的弹性集体模式不是由刚性晶体的振动产生的,而是由组成层之间的相对位移产生的。尽管它们与声学声子相似,但这些称为相位子的模式不受任何守恒定律的保护。在这里,我们表明,在层之间的相对取向和热波动与它们的滑动运动的无序降低了在莫尔超晶格中的声音的传播。具体而言,相位子模式在低能量下变得过阻尼,并获得有限的间隙,这显示出对扭转角方差的普遍依赖性。因此,扭转角的不均匀性不仅表现在莫尔系统的非相互作用电子结构中,而且表现在它们的类声子模式中。更广泛地说,我们的研究结果有重要的影响扭曲莫尔系统的电子特性是敏感的电子-声子耦合。

英文摘要:

The elastic collective modes of a moiré superlattice arise not from vibrations of a rigid crystal but from the relative displacement between the constituent layers. Despite their similarity to acoustic phonons, these modes, called phasons, are not protected by any conservation law. Here, we show that disorder in the relative orientation between the layers and thermal fluctuations associated with their sliding motion degrade the propagation of sound in the moiré superlattice. Specifically, the phason modes become overdamped at low energies and acquire a finite gap, which displays a universal dependence on the twist-angle variance. Thus, twist-angle inhomogeneity is manifested not only in the non-interacting electronic structure of moiré systems, but also in their phonon-like modes. More broadly, our results have important implications for the electronic properties of twisted moiré systems that are sensitive to the electron-phonon coupling.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑