Collective modes and gapped momentum states in liquid Ga: Experiment, theory, and simulation
R. M. Khusnutdinoff, Cillian Cockrell, Oliver A. Dicks, Anders C. S. Jensen, Manh Duc Le, Ling Wang, Martin T. Dove, А. В. Мокшин, В. В. Бражкин, Kostya Trachenko
Abstract
Collective excitations in liquids are important for understanding liquid dynamical and thermodynamic properties. Gapped momentum states (GMS) are a notable feature of liquid dynamics predicted to operate in the transverse collective excitations. Here, we combine inelastic neutron scattering experiments, theory, and molecular dynamics modeling to study collective excitations and GMS in liquid Ga in a wide range of temperature and $k$ points. We find that all three lines of enquiry agree for the longitudinal liquid collective dynamics. In the transverse collective dynamics, the experiments agree with theory, modeling, as well as earlier x-ray experiments at larger $k$, whereas theory and modeling agree in a wide range of temperature and $k$ points. We observe the emergence and development of the $k$ gap in the transverse dispersion relation which increases with temperature and inverse of relaxation time as predicted theoretically.