Mori Tatsuya, Jiang Yue, Fujii Yasuhiro, Kitani Suguru, Mizuno Hideyuki, Koreeda Akitoshi, Motoji Leona, Tokoro Hiroko, Shiraki Kentaro, Yamamoto Yohei, Kojima Seiji
Division of Materials Science, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan.
Department of Physical Sciences, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga 525-8577, Japan.
Phys Rev E. 2020 Aug;102(2-1):022502. doi: 10.1103/PhysRevE.102.022502.
The boson peak is a largely unexplained excitation found universally in the terahertz vibrational spectra of disordered systems; the so-called fracton is a vibrational excitation associated with the self-similar structure of monomers in polymeric glasses. We demonstrate that such excitations can be detected using terahertz spectroscopy. In the case of fractal structures, we determine the infrared light-vibration coupling coefficient for the fracton region and show that information concerning the fractal and fracton dimensions appears in the exponent of the absorption coefficient. Finally, using terahertz time-domain spectroscopy and low-frequency Raman scattering, we experimentally observe these universal excitations in a protein (lysozyme) system that has an intrinsically disordered and fractal structure and argue that the system should be considered a single supramolecule. These findings are applicable to amorphous and fractal objects in general and will be valuable for understanding universal dynamics of disordered systems via terahertz light.
玻色子峰是无序系统太赫兹振动光谱中普遍存在的一种 largely unexplained 激发；所谓的分形子是与聚合物玻璃中单体的自相似结构相关的一种振动激发。我们证明了可以使用太赫兹光谱检测到这种激发。在分形结构的情况下，我们确定了分形子区域的红外光 - 振动耦合系数，并表明有关分形维和分形子维的信息出现在吸收系数的指数中。最后，利用太赫兹时域光谱和低频拉曼散射，我们在具有内在无序和分形结构的蛋白质（溶菌酶）系统中通过实验观察到了这些普遍激发，并认为该系统应被视为单个超分子。这些发现一般适用于无定形和分形物体，对于通过太赫兹光理解无序系统的普遍动力学将具有重要价值。
