Magnetic field effect on low-energy spin excitations in a novel quantum spin liquid candidate

We plan to study the effect of magnetic field on the spin excitations in the newly discovered quantum spin liquid Na2BaCo(PO4)2. Our preliminary inelastic neutron scattering measurements on the powder sample reveals that the spin-excitation is continuum-type at base T (1K) without external field, with band-width in the order of 0.1 to 0.2 meV. With a large enough field above the critical value (Hc ~ 2T), the energy of the spin excitations is lifted. Most importantly, one could observe a possible dispersion suggesting well-defined excitations are induced by the field when the system is driven out of the quantum spin liquid state. We would like to study the effect of field on this material in more details with single crystal samples available in order to understand how the spin excitations change between a quantum spin liquid state and a disordered non-spin-liquid state.