Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan.
Phys Rev Lett. 2014 Mar 28;112(12):125702. doi: 10.1103/PhysRevLett.112.125702. Epub 2014 Mar 26.
Here, we study the phase transition kinetics in a supercooled liquid state of triphenyl phosphite by means of time-resolved polarized and depolarized light scattering to address a long-standing controversy on its mechanism, i.e., whether the phenomenon is primarily induced by liquid-liquid transition (LLT) or by nanocrystal formation. We find that the polarized scattering intensity exhibits a peak as a function of time, and its low wave number limit is nonzero for any annealing temperatures, both of which strongly indicate the nonconserved nature of an order parameter governing the transition. We also observe evolution of depolarized scattering. Above the spinodal temperature TSD, the depolarized scattering intensity monotonically increases with time since it is dominated by scattering from nanocrystallites, which are continuously formed during the process. Below TSD, on the other hand, it exhibits a distinct peak as a function of time as the polarized scattering intensity does. This appearance of the peak suggests that dielectric tensor fluctuations responsible for the depolarized scattering mainly come from isotropic density fluctuations and not from nanocrystallites, supporting the occurrence of LLT.
在这里，我们通过时间分辨的偏振和去偏振光散射研究三苯基膦酸酯在过冷液态中的相转变动力学，以解决其机制上的一个长期争议，即该现象主要是由液-液相转变（LLT）还是纳米晶形成引起的。我们发现，偏振散射强度随时间呈现峰值，并且其低波数极限对于任何退火温度都不为零，这两者都强烈表明控制相变的序参量不具有守恒性质。我们还观察到去偏振散射的演化。在旋节线温度 TSD 以上，由于去偏振散射主要来自纳米晶的散射，而纳米晶在过程中不断形成，因此随着时间的推移，去偏振散射强度单调增加。另一方面，在 TSD 以下，它随时间呈现出明显的峰值，如偏振散射强度一样。这种峰值的出现表明，负责去偏振散射的介电张量涨落主要来自各向同性密度涨落，而不是纳米晶，支持 LLT 的发生。
