Balz, C.; Lampen-Kelley, P.; Banerjee, A.; Yan, J.; Lu, Z.; Hu, X.; Yadav, S.M.; Takano, Y.; Liu, Y.; Tennant, D.A.; Lumsden, M.D.; Mandrus, D.; Nagler, S.E.: Finite field regime for a quantum spin liquid in α-RuCl3. Physical Review B 100 (2019), p. 060405(R)/1-6

An external magnetic field can induce a transition in α−RuCl3 from an ordered zigzag state to a disordered state that is possibly related to the Kitaev quantum spin liquid. Here, we present field-dependent inelastic neutron scattering and magnetocaloric effect measurements implying the existence of an additional transition out of the quantum spin-liquid phase at an upper field limit Bu. The neutron scattering shows three distinct regimes of magnetic response. In the low-field ordered state the response shows magnon peaks; the intermediate-field regime shows only continuum scattering, and above Bu the response shows sharp magnon peaks at the lower bound of a strong continuum. Measurable dispersion of magnon modes along the (0,0,L) direction implies non-negligible interplane interactions. Combining the magnetocaloric effect measurements with other data, a T−B phase diagram is constructed. The results constrain the range where one might expect to observe quantum spin-liquid behavior in α−RuCl3.