Meso-scale fluctuations in liquid chalcogens near the metal-nonmetal transition

Abstract

Liquid Te-Se mixtures exhibit a metal-nonmetal (M-NM) transition, which is accompanied by various anomalies in thermodynamic properties such as the thermal expansion coefficient, compressibility and sound attenuation coefficient. These anomalies may be explained by the coexistence and the relaxation of the metallic and non-metallic regions in the liquid, and it is interesting to study the space and time-structure of the meso-scale fluctuations. In the present work, we performed small angle neutron scattering (SANS) and neutron spin-echo (NSE) measurements for liquid Te-Se mixtures near the M-NM transition. We observed that SANS intensity increases with temperature. The NSE intermediate scattering function can be expressed by a superposition of fast and slow exponential relaxation process, whose relaxation times are estimated as Tfast ∼ 0.1nsec and Tslow > 10 nsec, respectively. The slow component becomes dominant in the low-Q region, and this process may be related to the anomalous sound attenuation.