Affiliations: Department of Applied Physics, Tohoku University, Sendai 980-8579, Japan | Department of Applied Chemistry, Hiroshima University, Higashi-hiroshima 739-8527, Japan | Institute for Solid State Physics, The University of Tokyo, Ibaraki 319-1106, Japan
Note: [] Corresponding author. Present address: Neutron Science Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki, 319-1195 Japan. E-mail: shamoto@neutrons.tokai.jaeri.go.jp
Abstract: Inelastic neutron scattering measurements have been performed on superconducting NaxHfNCl powder samples with x = 0.27 and 0.38 (Tc = 22 K): We have observed several temperature dependent phonon anomalies, e.g. at E ∼ 15, 29, 76, and 81 meV for the former sample. A phonon peak with E = 14.5 meV at Q ∼ 6Å−1 increases for both samples with decreasing temperature below T = 40 K; which is much higher than Tc. The phonon peak is assigned to an ab-plane vibrational mode, Eu, of chlorine and hafnium atoms, which strongly modifies the electronic band structure. The phonon anomaly is discussed in terms of carrier inhomogeneity.
Keywords: Inelastic neutron scattering, Phonon density of states, Double honeycomb lattice, Superconductor
