Temperature dependence of the normal state specific heat of κ-(BEDT-TTF) < inf > 2 < /inf > Cu(NCS) < inf > 2 < /inf >

Abstract

We report measurements of the normal state specific heat of κ-(BEDT-TTF)2Cu(NCS)2 from 300 K down to the onset of superconductivity. We find that previously reported Debye temperatures greatly overestimate the actual lattice contribution to the specific heat. Although the lattice vibrations are not well described using a single Debye oscillator for all the vibrational modes, they can be modeled by a Debye oscillator for the lowest energy BEDT-TTF ↔ BEDT-TTF inter-molecular vibrational mode plus a series of Einstein oscillators for the higher-energy intra-molecular optical modes.