Abstract
Two-dimensional triangular-lattice materials with spin-1/2 are perfect platforms for investigating quantum frustrated physics with spin fluctuations. Here we report the structure, magnetization, heat capacity, and inelastic neutron scattering (INS) results on cesium ytterbium diselenide, CsYbSe2. There is no long-range magnetic order down to 0.4 K at zero field. The temperature-dependent magnetization, M(T), reveals an easy-plane magnetic anisotropy. A maximum is found in M(T) around T≈1.5 K when magnetic field H is applied in the ab plane, indicating the short-range interaction. The low-temperature isothermal magnetization M(H) shows a one-third plateau of the estimated saturation moment, which is characteristic of a two-dimensional (2D) frustrated triangular lattice. Heat capacity shows field-induced long-range magnetic order for both H||c and H||ab directions. The broad peak in heat capacity and highly damped INS magnetic excitation at T=2 K suggests strong spin fluctuations. The dispersive in-plane INS, centered at the (1/3 1/3 0) point, and the absence of dispersion along the c direction suggest 120∘ noncollinear 2D-like spin correlations. All these results indicate that the two-dimensional frustrated material CsYbSe2 can be in proximity to the triangular-lattice quantum spin liquid. We propose an experimental low-temperature H−T phase diagram for CsYbSe2.
