Low-lying vibrational states in superconducting κ-(BEDT-TTF)2Cu(NCS)2: Inelastic neutron scattering

Abstract We report here two kinds of time-of-flight inelastic-neutron-scattering measurements using LAM-D and LAM-40 spectrometers on an aggregate of randomly oriented single crystals and a piece of single crystal, respectively, of hydrogenated κ-(h g -BEDT-TTF) 2 Cu(NCS) 2 . The generalized partial density-of-states spectrum shows an anomalous enhancement in low-lying energy regime below several meV at low temperatures below T c . It suggests that low-lying vibrational modes involving protons at terminal ethylenes appear in the superconducting phase.