Interplay between Hund's Coupling and Spin-Orbit Interaction on Elementary Excitations in Sr^sub 2^IrO^sub 4

We study the elementary excitations in 5d transition metal oxide ... by calculating the particle-hole Green's function within the random phase approximation on an antiferromagnetic ground state in the two-dimensional multi-orbital Hubbard model. The obtained magnetic excitations of bound states show a characteristic dispersion in consistent with the experiments. In addition, two new types of excitations are found due to the interplay between spin-orbit interaction and Hund's coupling: a magnetic excitation as a bound state, which has energy gap at the ... point, and an exciton as a resonant mode in the continuum of electron-hole pair creation. (ProQuest: ... denotes formulae/symbols omitted.)