TY - JOUR

T1 - Collective excitations in a two-dimensional antiferromagnet in a strong magnetic field

AU - Syromyatnikov, A. V.

PY - 2009

Y1 - 2009

N2 - We discuss spin-1/2 two-dimensional 2D Heisenberg antiferromagnet AF on a square lattice at T=0 in strong magnetic field H near its saturation value Hc. 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 (Hc−H)/Hc. We find that magnons are well-defined quasiparticles at H>0.9Hc although the damping is quite large near the zone boundary. A characteristic rotonlike local minimum in the spectrum is observed at k= (\pi,\pi), accompanied by a decrease in the damping near k= (\pi,0). The suggested approach can be used in discussion of shortwavelength excitations in other 2D Bose gases of particles or quasiparticles.

AB - We discuss spin-1/2 two-dimensional 2D Heisenberg antiferromagnet AF on a square lattice at T=0 in strong magnetic field H near its saturation value Hc. 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 (Hc−H)/Hc. We find that magnons are well-defined quasiparticles at H>0.9Hc although the damping is quite large near the zone boundary. A characteristic rotonlike local minimum in the spectrum is observed at k= (\pi,\pi), accompanied by a decrease in the damping near k= (\pi,0). The suggested approach can be used in discussion of shortwavelength excitations in other 2D Bose gases of particles or quasiparticles.

U2 - DOI: 10.1103/PhysRevB.79.054413

DO - DOI: 10.1103/PhysRevB.79.054413

M3 - статья

VL - 79

SP - 054413_1-6

JO - Physical Review B-Condensed Matter

JF - Physical Review B-Condensed Matter

SN - 1098-0121

IS - 5

ER -