论文标题
拉曼散射与红外激发与摩西共鸣$ _2 $间接乐队差距
Raman Scattering with infrared excitation resonant with MoSe$_2$ indirect band gap
论文作者
论文摘要
共振拉曼散射（探测电子，声子及其相互作用的晶体）被广泛用于二维材料中。在这里，我们调查了Mose中的拉曼模式$ _2 $在不同的激光激发能量从2.33 eV到接近红外1.16 eV。 1.16 EV激发能量的拉曼光谱表明，与摩西$ _2 $间接频段隙相比，如果与一阶语音模式强度相比，高阶模式的强度会得到强烈增强。通过将实验结果与用密度功能理论计算的状态的两次量子密度进行比较，我们表明高阶模式主要源自具有相反动量的两种频率模式。特别是，我们确定了声子模式的力量，这些模式与电子强烈吻合以在1.16 eV下产生共振过程，而我们验证在2.33 eV时，两声模式线形与在整个Brillouin区域中计算出的状态的两频密度很好地比较。我们还表明，通过降低晶体温度，我们积极抑制了谐振剂两光模式的强度，并将其解释为低温下间接带隙的增加，从而使我们的激发能将我们的激发能移出谐振条件。
Resonance Raman scattering, which probes electrons, phonons and their interplay in crystals, is extensively used in two-dimensional materials. Here we investigate Raman modes in MoSe$_2$ at different laser excitation energies from 2.33 eV down to the near infrared 1.16 eV. The Raman spectrum at 1.16 eV excitation energy shows that the intensity of high-order modes is strongly enhanced if compared to the first-order phonon modes intensity due to resonance effects with the MoSe$_2$ indirect band gap. By comparing the experimental results with the two-phonon density of states calculated with density functional theory, we show that the high-order modes originate mostly from two-phonon modes with opposite momenta. In particular, we identify the momenta of the phonon modes that couple strongly with the electrons to produce the resonance process at 1.16 eV, while we verify that at 2.33 eV the two-phonon modes lineshape compares well with the two-phonon density of state calculated over the entire Brillouin Zone. We also show that, by lowering the crystal temperature, we actively suppress the intensity of the resonant two-phonon modes and we interpret this as the result of the increase of the indirect band gap at low temperature that moves our excitation energy out of the resonance condition.
