Glassy-like thermodynamical properties of (TMTSF)2PF6

We report on specific heat measurements of (TMTSF)2PF6 between 0.1 and 25 K. In addition to the small anomaly at the SDW transition temperature, this SDW compound exhibits all characteristics of the low temperature thermodynamical properties of CDW systems. These typical features are additional excitations to regular phonons contributing to the specific heat below 0.5 K which are reminiscent of low-energy excitations in glasses and the enthalpy relaxation exhibiting aging effects such as in other disordered systems. Finally, the role of the isothermal annealing and the kinetics of measurements on the specific heat anomaly in the range 2.5–5 K are indicative of a glass transition in the general frame of freezing of supercooled liquids.