We study one- and two-magnon excitations above the fully polarized state of the spin-
1/2 triangular-lattice
J1-
J2-
J3 Heisenberg model with a uniform scalar-chirality interaction. In the Heisenberg model, we identify two special manifolds of one-magnon minima by rewriting the dispersion in complete-square form. The chirality term cancels exactly in the one-magnon sector, leaving the dispersion and instability field unchanged, but survives in the two-magnon sector as an oriented interaction between neighboring magnons. Using symmetry-adapted lattice harmonics, we show that scalar chirality splits two-magnon states of opposite relative-motion chirality and selectively enhances the binding of one of them. It can strengthen an existing bound state, change the symmetry of the lowest magnon pair, or induce binding where none occurs without chirality. Exact diagonalization further shows that two-magnon pairing can also occur at finite total momentum. Our results identify scalar chirality as a microscopic mechanism for enhancing two-magnon pairing without modifying the one-magnon spectrum.
Employing exact diagonalization, we systematically study the anisotropic Heisenberg model which is related to rare-earth triangular-lattice materials. We probe its full 3D phase diagram afresh and identify a large region of quantum spin liquid (QSL) phase which can extend to the QSL region of the
J1–J2 triangular Heisenberg model. Furthermore, we explore the magnetization curves of different phases and reproduce the 1/3-magnetization plateau in the quantum spin liquid phase region. More importantly, to study the possible chemical disorders in real materials, we consider the randomness of exchange interactions and find no spin glass order. And there is a large region of random-singlet phase which contains strongly random spin networks, dominated by two-spin singlets, four-spin singlets and other singlet domains. Our comprehensive ED study can give detailed insightful understanding of the microscopic Hamiltonian related to the
YbMgGaO4 and some other related rare-earth triangular-lattice materials.