Elementary excitations in the ordered phase of spin-1/2 J(1)-J(2) model on square lattice

Article

关键词: HEISENBERG-ANTIFERROMAGNET;    VALENCE-BOND;    EXPANSION;    DYNAMICS;   

DOI  :  10.1103/PhysRevB.99.224402

来源: SCIE

【 摘 要 】

We use the recently proposed four-spin bond-operator technique (BOT) to discuss the spectral properties of a frustrated spin-1/2 J(1)-J(2) Heisenberg antiferromagnet on a square lattice at J(2) < 0.4J(1) (i.e., in the Neel ordered phase). This formalism is convenient for the consideration of low-lying excitations which appear in conventional approaches as multimagnon bound states (e.g., the Higgs excitation) because separate bosons describe them in the BOT. At J(2) = 0, the obtained magnon spectrum describes accurately available experimental data. However, calculated one-magnon spectral weights and the transverse dynamical structure factor (DSF) do not reproduce experimental findings quantitatively around the momentum k = (pi, 0). Thus, we do not support the conjecture that the continuum of excitations observed experimentally and numerically near k = (pi, 0) is of the Higgs-magnon origin. Upon J(2) increasing, one-magnon spectral weights decrease, and spectra of high-energy spin-0 and spin-1 excitations move down. One of the spin-0 quasiparticles becomes long-lived, and its spectrum merges with the magnon spectrum in the majority of the Brillouin zone at J(2) approximate to 0.3J(1). We predict also that the Higgs excitation and another spin-0 quasiparticle become long-lived around k = (pi/2, pi/2) at J(2) greater than or similar to 0.3J(1) and produce sharp anomalies in the longitudinal DSF.

【 授权许可】

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