Quantum entanglement of XY-type spin dimers on Shastry-Sutherland lattice

The 2D Shastry–Sutherland materials have provided paradigmatic examples of a variety of exotic states of matter arising from their distinctive arrangement of spin dimers. Exotic magnetic states such as quantum spin liquids (QSLs) and plaquette-singlet states have been proposed to explain the fractionalized magnetization plateaux. These states have produced a rich phase diagram that serves as an important roadmap for discovering emerging new theories. So far, all known Shastry–Sutherland systems exhibit either Heisenberg- or Ising-type exchange interactions. In this talk, I will present experimental data and theoretical simulations on two rare-earth Shastry–Sutherland materials, BaCe₂ZnS₅[1] and Yb₂Be₂SiO₇[2], that exhibit anisotropic XY-type interactions. Through fitting neutron spectroscopy and thermodynamic data, we were able to exactly solve the ground state of these rare-earth Shastry–Sutherland systems and reveal an unusual, ferromagnetically entangled ground state that does not fall into the traditional singlet-triplet picture. The entangled ground state also suggests that a quantum phase transition can be induced through an applied magnetic field, allowing the system to enter a more complex, interactive regime.