Article: published in Physical Review Letters by M. A. Ramos, IFIMAC researcher.
The low temperature thermal and transport properties of an unusual kind of a crystal which exhibits minimal molecular positional and tilting disorder have been measured in this work, as well as inelastic neutron scattering spectra. The material, namely the low-dimensional, highly anisotropic pentachloronitrobenzene (PCNB) exhibits a layered structure of rhombohedral parallel planes in which the molecules execute large-amplitude in-plane as well as concurrent out-of-plane librational motions. Our study reveals that the universal low-temperature glassy anomalies can be found in a system with minimal disorder as that due to the freezing of mostly in-plane reorientational jumps of molecules between crystallographic equivalent positions with partial site occupation. Our findings will pave the way to a deeper understanding of the origin of above-mentioned universal glassy properties. [Full article]