Spin wave dispersion, including possible quantum effect, of Kagome spin ice HoAgGe by inelastic neutron scattering

Spin ices are exotic phases of matter characterized by frustrated spins obeying local ice rules, that minimize the number of spatially isolated magnetic monopoles, in analogy with the electric dipoles in water ice. In two dimensions, one can similarly define ice rules for in-plane Ising spins arranged on a kagome lattice, leading to a variety of unique orders and excitations. Based on neutron results, HoAgGe is the first compound to realize classical kagome spin ice state. Clear spin wave excitations appear at 1.5 K on randomly oriented single crystals. The spin wave has a small gap about 0.2 meV, indicating Ising anisotropy in spin Hamiltonian. We plan to conduct inelastic neutron scattering on properly oriented crystals to collect information on exchange coupling strength, and the possible quantum effect with field along c axis, namely perpendicular to the kagome plane of Ho spins.