Crystalline electric field excitations in the quantum spin liquid candidate <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>NaYbSe</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>

Very recently we revealed a large family of triangular lattice quantum spin liquid candidates named rare-earth chalcogenides, which features high-symmetry structure without structural/charge disorders and impurities, may serve as an ideal platform exploring physics. The knowledge crystalline electric-field (CEF) excitations is essential step to explore the fundamental magnetism systems. Here employed inelastic neutron scattering (INS) Raman (RS) carry out comprehensive CFE investigation on $NaYbSe_{2}$, promising representative family. By comparison with its nonmagnetic compound $NaLuSe_{2}$, are able identify CEF at 15.8, 24.3 30.5 meV 5K. selected cuts INS spectra well re-produced anisotropy $g$ factors ($g_{ab}:g_{c}\sim3:1$). Further, explained by our calculations based point charge model. Interestingly, $NaYbSe_{2}$ exhibits unusual shift higher energies increasing temperatures, mode close first excitation shows anomalously softening decreasing temperatures. absence anomalies in $NaLuSe_{2}$ clearly demonstrates CEF-phonon coupling not reported It can be understood term weaker electronegativity Se. fact that smallest sub-family $NaYbCh_{2}$ $\sim$ 180K (Ch=O, S, Se), guarantees strictly described effective S=1/2 picture sufficiently low Interestingly here present alternative possibilities manipulate