Low-energy dynamics of superionic conductor AgI investigated by inelastic neutron scattering measurements

Nakamura, Mitsutaka   ; Shimakura, Hironori; Ueno, Hiroki; Kawakita, Yukinobu  ; Arai, Masatoshi; Kawamura, Seiko   ; Nakajima, Kenji  ; Kikuchi, Tatsuya  

In order to elucidate the dynamical changes caused by differences in the structural phase of AgI which is a typical superionic conducting material, we carried out a detailed examination of the dynamical structure factor S(Q,E) obtained by inelastic neutron scattering measurements. Herein, we show that the intensity in a low-energy region (E 2 meV) at around 2 abruptly increases beyond 420 K, and the temperature-dependent behavior of this intensity is remarkably similar to that of dc ionic conductivity over a wide temperature range in the region of 420 K. A unified explanation of the ionic conduction mechanism in superionic materials may be established in terms of their characteristic low-energy excitations.