Magnetism of NaYbS_(2):From finite temperatures to ground state

Rare-earth chalcogenide compounds ARECh_(2)(A=alkali or monovalent metal,RE=rare earth,Ch=O,S,Se,Te)are a large family of quantum spin liquid(QSL)candidate materials.NaYbS2is a representative member of the family.Several key issues on NaYbS_(2),particularly how to determine the highly anisotropic spin Hamiltonian and describe the magnetism at finite temperatures and the ground state,remain to be addressed.In this paper,we conducted an in-depth and comprehensive study on the magnetism of NaYbS_(2) from finite temperatures to the ground state.Firstly,we successfully detected three crystalline electric field(CEF)excitation energy levels using low-temperature Raman scattering technique.Combining them with the CEF theory and magnetization data,we worked out the CEF parameters,CEF energy levels,and CEF wavefunctions.We further determined a characteristic temperature of~40 K,above which the magnetism is dominated by CEF excitations while below which the spinexchange interactions play a main role.The characteristic temperature has been confirmed by the temperature-dependent electron spin resonance(ESR)linewidth.Low-temperature ESR experiments on the dilute magnetic doped crystal of NaYb_(0.1)Lu_(0.9)S_(2) further helped us to determine the accurate g-factor.Next,we quantitatively obtained the spin-exchange interactions in the spin Hamiltonian by consistently simulating the magnetization and specific heat data.Finally,the above studies allow us to explore the ground state magnetism of NaYbS_(2) by using the density matrix renormalization group.We combined numerical calculations and experimental results to demonstrate that the ground state of NaYbS_(2) is a Dirac-like QSL.