Static and dynamic properties of Kitaev-Heisenberg ferromagnet on a triangular lattice

We present an extensive study of ground state and excitations of ferromagnetic anisotropic-exchange Kitaev-Heisenberg model on a triangular lattice using order-by-disorder calculations. It is shown that while bond-dependent terms do not affect the ground state classically, quantum fluctuations select preferred magnetization direction of the ferromagnetic state. Anisotropic terms of the magnetic Hamiltonian also give rise to magnon-magnon interactions that lead to spontaneous decays and spectral renormalization, which we illustrate using non-linear spin-wave theory.