Field effect of the magnetic ground state in a triangular-lattice magnet

Rare-earth frustrated magnets have attracted great interest because they can form rather complex ground states such as hidden order phases, the order parameters of which cannot be disclosed by conventional magnetic probes including the neutron diffraction experiments. Our recent LET experiments on a triangular-lattice magnet TmMgGaO4 revealed an exotic intertwined multipolar and dipolar order under zero magnetic field. The dipolar order is caught by the neutron diffraction and the quantum fluctuation of the multipolar moments leads to the sharp spin wave. Moreover, it has been proposed that the magnetic field will tune the multipolar order and its quantum excitations will be modified. Here we propose to study the spin excitations of TmMgGaO4 under various magnetic fields so that the field dependent evolution of the hidden order and its quantum excitations can be decided.