MoS2中多声子谱的综合分析
A Comprehensive Multiphonon Spectral Analysis in MoS2
摘要：
本文对块状和单层MoS2进行了全面的多声子拉曼和互补红外分析。对于块状MoS2，分析包括对称性分配，从中我们获得了一组广泛的允许的二级跃迁在高对称性的M，K和γ布里渊区点。在激发能为1.96 eV的低温（95 K）共振喇曼谱中，提出了约80个直至5级喇曼过程的跃迁归属。我们认为主要贡献来自四个声子：A1g（M），E12g（M2），E22g（M1）（TA '（M））和E22g（M2）（LA'（M））.最后三个是M处的单简并声子，其起源是E12g（伽马）和E22g（伽马）声子。在这四个声子中，我们在共振拉曼光谱中识别出所有（除了一个）的二阶泛音、组合带和差带以及许多三阶带。与在M点处仅允许具有相同反转对称性（g或u）的组合的预期一致，与LA（M）声子的组合的贡献不能用上述四个声子来考虑。虽然很小，但K点和可能的伽马点声子的贡献也很明显。在非共振条件下测得的2LA带与最近发表的两个声子态密度之间的惊人相似性支持下，我们提出先前归属于2LA（M）的带的下半部分是由于K和M之间的van Hove奇异性引起的。较高的部分，以前只归因于A2u（γ）声子，主要是由于在M的LA和LA'声子。对于单层MoS2，从M和γ布里渊区点的二阶声子过程也进行了分析，并在类似的框架内讨论的散装。
英文摘要：
We present a comprehensive multiphonon Raman and complementary infrared analysis for bulk and monolayer MoS2.For the bulk the analysis consists of symmetry assignment from which we obtain a broad set of allowed second order transitions at the high symmetry M,K and gamma Brillouin zone points. The attribution of about 80 transitions of up to fifth order Raman processes are proposed in the low temperature(95K)resonant Raman spectrum measured with the excitation energy of 1.96 eV,which is slightly shifted from the A exciton. We propose that the main contributions come from four phonons:A1g(M),E12g(M2),E22g(M1)(TA'(M))and E22g (M2)(LA'(M)). The last three are single degenerate phonons at M with an origin of the E12g(gamma)and E22g(gamma)phonons. Among the four phonons, we identify in the resonant Raman spectra all(but one) of the second order overtones,combination and difference bands and many of the third order bands. Consistent with the expectation that at the M point only combinations with the same inversion symmetry (g or u)are Raman allowed, the contribution of combinations with the LA(M)phonon can not be considered with the above four phonons. Although minor,contribution from K point and possibly gamma point phonons are also evident. The "2LA band",measured at ~460 cm-1 is reassigned.Supported by the striking similarity between this band, measured under off resonant conditions, and recently published two phonon density of states, we propose that the lower part of the band,previously attributed to 2LA(M),is due to a van Hove singularity between K and M. The higher part,previously attributed exclusively to the A2u(gamma)phonon,is mostly due to the LA and LA' phonons at M. For the monolayer MoS2, the second order phonon processes from M and gamma Brillouin zone points are also analyzed and are discussed within similar framework to that of the bulk.
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。
