Determination of spin Hamiltonian for an ideal triangular lattice of Yb in NaBaYb(BO₃)₂

In the search for materials with a quantum spin liquid phase, the triangular lattice of Yb is of interest. Frustration combined with the ability of the Kramers ion Yb³⁺ to form a pseudo spin-1/2 degree of freedom, may provide favorable conditions for a quantum spin liquid. Here we study NaBaYb(BO₃)₂, which contains high quality triangular layers of Yb³⁺. One layer is sandwiched between two layers of Na⁺, the other between two layers of Ba²⁺.  Low temperature heat capacity measurements indicate the inter-site interactions are in the same range as magnetic dipole interactions [1]. Here we determine the Hamiltonian that describes the low temperature magnetism of NaBaYb(BO₃)₂. We used Raman Spectroscopy and Inelastic Neutron Scattering to determine the crystal field level scheme and the ground state wavefunction for Yb³⁺.The Numerical Linked Cluster method was used to analyze the low field thermodynamic data and obtain estimates for the inter-site interactions.