TY - JOUR

T1 - Elementary excitations in the ordered phase of spin-1/2 J1–J2 model on square lattice

AU - Syromyatnikov, A. V.

AU - Aktersky, A. Yu.

PY - 2019

Y1 - 2019

N2 - We use the recently proposed four-spin bond-operator technique (BOT) to discuss the spectral properties of a frustrated spin-12 J1-J2 Heisenberg antiferromagnet on a square lattice at J2<0.4J1 (i.e., in the Néel 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 J2=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=(π,0). Thus, we do not support the conjecture that the continuum of excitations observed experimentally and numerically near k=(π,0) is of the Higgs-magnon origin. Upon J2 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 J2≈0.3J1. We predict also that the Higgs excitation and another spin-0 quasiparticle become long-lived around k=(π/2,π/2) at J2 0.3J1 and produce sharp anomalies in the longitudinal DSF.

AB - We use the recently proposed four-spin bond-operator technique (BOT) to discuss the spectral properties of a frustrated spin-12 J1-J2 Heisenberg antiferromagnet on a square lattice at J2<0.4J1 (i.e., in the Néel 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 J2=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=(π,0). Thus, we do not support the conjecture that the continuum of excitations observed experimentally and numerically near k=(π,0) is of the Higgs-magnon origin. Upon J2 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 J2≈0.3J1. We predict also that the Higgs excitation and another spin-0 quasiparticle become long-lived around k=(π/2,π/2) at J2 0.3J1 and produce sharp anomalies in the longitudinal DSF.

KW - HEISENBERG-ANTIFERROMAGNET

KW - VALENCE-BOND

KW - EXPANSION

KW - DYNAMICS

UR - http://www.scopus.com/inward/record.url?scp=85067208042&partnerID=8YFLogxK

U2 - 10.1103/PhysRevB.99.224402

DO - 10.1103/PhysRevB.99.224402

M3 - Article

VL - 99

JO - Physical Review B-Condensed Matter

JF - Physical Review B-Condensed Matter

SN - 1098-0121

IS - 22

M1 - 224402

ER -