Collective excitations in two-dimensional antiferromagnet in strong magnetic field

Abstract

We discuss spin-$\frac{1}{2}$ two-dimensional (2D) Heisenberg antiferromagnet (AF) on a square lattice at T=0 in strong magnetic field H near its saturation value $H_c$. A perturbation approach is proposed to obtain spectrum of magnons with momenta not very close to AF vector in the leading order in small parameter $(H_c-H)/H_c$. We find that magnons are well-defined quasi-particles at $H>0.9H_c$ although the damping is quite large near the zone boundary. A characteristic rotonlike local minimum in the spectrum is observed at $\mathbf{k}=(\pi ,0)$ accompanied by decrease of the damping near $(\pi ,0)$. The suggested approach can be used in discussion of short-wavelength excitations in other 2D Bose gases of particles or quasi-particles.

8 pages, 5 figures. Final version

References in corpus (6)

• Excitation spectra of the spin-1/2 triangular-lattice Heisenberg antiferromagnet
• Quantum dynamics and entanglement of spins on a square lattice
• Magnon Decay in Noncollinear Quantum Antiferromagnets
• Flat spin wave dispersion in a triangular antiferromagnet
• Magnetic order in the S=1/2 two-dimensional molecular antiferromagnet, copper pyrazine perchlorate Cu(Pz)_2(ClO_4)_2
• Numerical evidence for unstable magnons at high fields in the Heisenberg antiferromagnet on the square lattice

Cited by in corpus (5)

• Spontaneous Magnon Decays
• Field-induced decay dynamics in square-lattice antiferromagnet
• Dynamical structure factor of quasi-2D antiferromagnet in high fields
• Multiple magnon modes in spin-1/2 Heisenberg antiferromagnet on simple square lattice in strong magnetic field
• Spin-flop transition accompanied with changing the type of magnetic ordering