Novel elementary excitations in spin-1/2 antiferromagnets on the triangular lattice

Abstract

We discuss spin-$\frac{1}{2}$ Heisenberg antiferromagnet on the triangular lattice using the recently proposed bond-operator technique (BOT). We use the variant of the BOT which takes into account all spin degrees of freedom in the magnetic unit cell containing three spins. Apart from conventional magnons known from the spin-wave theory (SWT), there are novel high-energy collective excitations in the BOT which are built from high-energy excitations of the magnetic unit cell. We obtain also another novel high-energy quasiparticle which has no counterpart not only in the SWT but also in the harmonic approximation of the BOT. All observed elementary excitations produce visible anomalies in dynamical spin correlators. We show that quantum fluctuations considerably change properties of conventional magnons predicted by the SWT. The effect of a small easy-plane anisotropy is discussed. The anomalous spin dynamics with multiple peaks in the dynamical structure factor is explained that was observed recently experimentally in $\mathrm{B}{\mathrm{a}}_3\mathrm{CoS}{\mathrm{b}}_2{\mathrm{O}}_9$ and which the SWT could not describe even qualitatively.

14 pages, 10 figures

References in corpus (15)

• Spontaneous Magnon Decays
• Fractional excitations in the square-lattice quantum antiferromagnet
• Anomalous High-Energy Spin Excitations in La2CuO4
• Excitation spectra of the spin-1/2 triangular-lattice Heisenberg antiferromagnet
• Spin excitations in a single La${}_2$CuO${}_4$ layer
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• Magnon Decay in Noncollinear Quantum Antiferromagnets
• Flat spin wave dispersion in a triangular antiferromagnet
• The antiferromagnetic spin-1/2 Heisenberg model on the square lattice in a magnetic field
• Avoided quasiparticle decay and enhanced excitation continuum in the spin-1/2 near-Heisenberg triangular antiferromagnet Ba3CoSb2O9
• Numerical evidence for unstable magnons at high fields in the Heisenberg antiferromagnet on the square lattice
• Elementary excitations in the ordered phase of spin-1/2 J1-J2 model on square lattice
• Chiral fluctuations in triangular antiferromagnets at $T\ll T_N$
• Multiple magnon modes in spin-1/2 Heisenberg antiferromagnet on simple square lattice in strong magnetic field

Cited by in corpus (8)

• Spin Excitation Spectra of Anisotropic Spin-$1/2$ Triangular Lattice Heisenberg Antiferromagnets
• Field-Induced Spin Excitations in the Spin-1/2 Triangular-Lattice Antiferromagnet CsYbSe${}_2$
• Complete field-induced spectral response of the spin-1/2 triangular-lattice antiferromagnet CsYbSe${}_2$
• Evidence of Two-Spinon Bound States in the Magnetic Spectrum of Ba${}_3$CoSb${}_2$O${}_9$
• Unusual dynamics of spin-1/2 antiferromagnets on the triangular lattice in magnetic field
• Dynamics of spin-1/2 $J_1$-$J_2$ model on the triangular lattice
• Thermal features of Heisenberg antiferromagnets on edge- versus corner-sharing triangular-based lattices: A message from spin waves
• Elementary excitations in undoped layered cuprates