Magnetic Frustration in CuYbSe₂: an Yb-Based Triangular Lattice Selenide

The Yb based triangular lattice delafossites AYbX₂ (A = alkali metal, X = O, S, Se) have recently been studied as quantum spin liquid candidates. We report the synthesis of powders and single crystals of CuYbSe₂ with a perfect triangular lattice of Yb³⁺ moments. Magnetic susceptibility and heat capacity measurements reveal no evidence of long-range magnetic ordering down to $1.8$~K in spite of a significant antiferromagnetic exchange between Yb³⁺ moments, suggesting a frustrated magnetic system. Electrical resistivity measurements indicate insulating behavior, consistent with the localized nature of magnetic moments. Heat capacity reveals that CuYbSe₂ can be treated as an effective spin $S = 1/2$ triangular lattice antiferromagnet below ~ 50~K. Magnetic susceptibility measurements on single crystals reveals weak magnetic anisotropy. These properties position CuYbSe₂ as a promising candidate for a quantum spin liquid state and as a new platform for exploring exotic magnetic ground states in triangular lattice systems.