Thermodynamic properties of glassy phonon states induced by strong electron correlations in 𝜃-type organic charge transfer salts

Abstract

The appearance of electron correlations–induced glassy state of low-energy phonons in the non-dimeric organic charge transfer salt in [Formula: see text]-(BEDT-TTF)2CsZn(SCN)4 is considered as a strong evidence of charge lattice coupling in molecular charge transfer salts. We discuss the temperature and the magnetic field dependences of the heat capacity of this salt in terms of the soft potential model to describe the thermodynamic properties of enhanced phonons that occur in molecular glasses. The evaluated [Formula: see text] term of [Formula: see text]-(BEDT-TTF)2CsZn(SCN)4 is about 30 mJ K[Formula: see text] mol[Formula: see text], which is much larger than other charge transfer salts described by the low-temperature approximation of the Debye model. The magnetic fields dependence of the boson peak is almost negligible, but the low-energy term, for example, in the temperature-linear term of heat capacity shows a slight change, probably due to the small amount of localized spin moments. The comparison with other systems is also performed.