Optical-Phonon Resonances with Saddle-Point Excitons in Twisted-Bilayer Graphene
Optical-Phonon Resonances with Saddle-Point Excitons in Twisted-Bilayer Graphene
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DOI：
10.1021/nl502412g
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发表时间：
2014-10-01
期刊：
影响因子：
10.8
通讯作者：
Novotny, Lukas
中科院分区：
文献类型：
--
作者：
Jorio, Ado;Kasperczyk, Mark;Novotny, Lukas
扭曲双层石墨烯（tBLG）在态密度中表现出货车霍韦奇异性，其可以通过改变扭曲角θ来调节。一个θ定义的tBLG已被生产和其特征在于与光学反射率和共振拉曼散射。θ工程的光学响应被证明是一致的持久的鞍点激子。由于二维鞍点激子的尖锐性，可以实现与斯托克斯和反斯托克斯拉曼散射分量的单独共振，类似于先前对一维碳纳米管观察到的。斯托克斯和反斯托克斯发射的激发功率依赖性表明这两个过程是相关的，并且它们共享相同的声子。
Twisted-bilayer graphene (tBLG) exhibits van Hove singularities in the density of states that can be tuned by changing the twisting angle theta. A theta-defined tBLG has been produced and characterized with optical reflectivity and resonance Raman scattering. The theta-engineered optical response is shown to be consistent with persistent saddle-point excitons. Separate resonances with Stokes and anti-Stokes Raman scattering components can be achieved due to the sharpness of the two-dimensional saddle-point excitons, similar to what has been previously observed for one-dimensional carbon nanotubes. The excitation power dependence for the Stokes and anti-Stokes emissions indicate that the two processes are correlated and that they share the same phonon.