Low-temperature specific heat of amorphous, orientational glass, and crystal phases of ethanol

Abstract

We have measured the specific heat between 0.5 and 20 K for three different solid phases of ethanol: the stable monoclinic crystal, the structural (amorphous) glass, and an orientationally disordered cubic crystalline phase (also named as orientational glass or ``glassy crystal''). We have therefore extended previous experiments on ethanol down to temperatures low enough as to investigate the region typically dominated in glasses by two-level-systems excitations or tunneling states. It is found that the orientational glass (i.e., a disordered crystal) of ethanol exhibits the same linear-term coefficient in the specific heat, and hence the same density of tunneling states, than the true, structural glass (i.e., an amorphous solid). In addition, combining specific-heat measurements in both deuterated and hydrogenated ethanol has allowed us to study the isotopic effect on these universal glassy properties, as well as on the Debye coefficients.