Specific heat of the organic metal bis(tetrathiotetracene) tri-iodide from 20 to 100 K, the vicinity of the metal-nonmetal phase transition

Abstract

Specific-heat measurements on pressed pellet samples of highly disordered bis(tetrathiotetracene) tri-iodide (TT${\mathrm{T}}_{2}$${\mathrm{I}}_{3}$) have been made from 20 to 100 K using thermal relaxation methods. An anomaly at 50 K in the form of a broad bump is reported which is coincident with magnetic susceptibility structure and occurs approximately 25 K above anomalies in electrical and optical behavior. The specific-heat discontinuity is consistent with a mean-field model for a Peierls phase transition with correction for fluctuations.