Effective Hamiltonian and low-lying eigenenergy clustering patterns of four-sublattice antiferromagnets

Article

关键词: HEISENBERG ANTIFERROMAGNETS;    TRIANGULAR LATTICE;    GROUP-SYMMETRY;    SPIN SYSTEMS;    DISORDER;    ORDER;    MODEL;    INTERFERENCE;    MOLECULES;    SPECTRA;   

DOI  :  10.1103/PhysRevB.65.064427

来源: SCIE

【 摘 要 】

We study the low-lying eigenenergy clustering patterns of quantum antiferromagnets with p sublattices (in particular p = 4). We treat each sublattice as a large spin, and using second-order degenerate perturbation theory, we derive the effective (biquadratic) Hamiltonian coupling the p large spins. In order to compare with exact diagonalizations, the Hamiltonian is explicitly written for a finite-size lattice, and it contains information on energies of excited states as well as the ground state. The result is applied to the face-centered-cubic Type-I antiferromagnet of spin 1/2, including second-neighbor interactions. A 32-site system is exactly diagonalized, and the energy spectrum of the low-lying singlets follows the analytically predicted clustering pattern.

【 授权许可】

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