Nondegenerate Chiral Phonons in Graphene/Hexagonal Boron Nitride Heterostructure from First-Principles Calculations,Nano Letters

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Nondegenerate Chiral Phonons in Graphene/Hexagonal Boron Nitride Heterostructure from First-Principles Calculations
Nano Letters ( IF 9.6 ) Pub Date : 2018-06-25 00:00:00 , DOI: 10.1021/acs.nanolett.8b01487
Mengnan Gao ₁ , Wei Zhang _{1,

2} , Lifa Zhang ₁

Affiliation

Triggered by the recent successful observation of previously predicted phonon chirality in the monolayer tungsten diselenide [ Science 2018, 359, 579], we systematically study the chiral phonons in the classical heterostructure of graphene/hexagonal boron nitride (G/h-BN) by first-principles calculations. It is found that the broken inversion symmetry and the interlayer interaction of G/h-BN not only open the phononic gaps but also lift the degeneracy of left-handed and right-handed chiral phonons at the first-Brillouin-zone corners (valleys). At valleys, the hybridization makes chiral phonon modes solely contributed from one individual layer. Moreover, we demonstrate that the vertical stress is effective to tune the degenerated phononic gap while keeping the valley-phonon chirality of G/h-BN heterostructure, which is favorable for the Raman or ultrafast infrared spectroscopy measurement. We also analyze the pseudoangular momentum of valley-phonon modes, which provide important references for the excitation and measurement of the chiral phonons in the process of electronic intervalley scattering. Collectively, our results on the chiral phonons in the G/h-BN heterostructure system could stimulate more experimental and theoretical studies and promote the future applications on the phonon-chirality-based phononics.

中文翻译：

从第一性原理计算石墨烯/六方氮化硼异质结构中的非简并手性声子

通过在单层二硒化钨[先前预测的声子手性的最近成功的观测触发科学 2018，359，579]，系统地研究的手性声子在石墨烯/六方氮化硼的经典异质结构（G / ħ -BN）通过第一-原理计算。发现破碎的反演对称性和G / h的层间相互作用-BN不仅打开了声子间隙，而且还提升了第一个布里渊区角（谷）处左手和右手手性声子的简并性。在山谷，杂交使手性声子模仅由一个单独的层贡献。此外，我们证明了垂直应力在保持G / h -BN异质结构的谷-声子手性的同时有效地调节了退化的声子间隙，这对于拉曼光谱或超快红外光谱测量是有利的。我们还分析了谷-声子模的拟角动量，这为电子区间激子散射过程中手性声子的激发和测量提供了重要的参考。总的来说，我们在G / h中的手性声子的结果-BN异质结构体系可以激发更多的实验和理论研究，并促进基于声子-手性的声子学的未来应用。

更新日期：2018-06-25

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