Quantum corrections to the spin-wave spectrum of La2 Cu O4 in an external magnetic field

The effects of quantum fluctuations on the magnetic field dependence of the spin-wave gaps in the lamellar antiferromagnet La2 Cu O4 are considered. Nonlinear corrections to the spin-wave spectrum are calculated to leading order in 1 S, where S is the localized spin. The nearest-neighbor exchange interactions between the Cu spins as well as the Dzyaloshinskii-Moriya interactions are taken into account. Using the experimental values of the components of the g -factor tensor, we get satisfactory agreement with the experimental results for the field dependence of the gaps by Gozar [Phys. Rev. Lett. 93, 027001 (2004)] and obtain consistent values of the in-plane and interplane coupling constants. The field dependence of the dispersion of spin waves propagating perpendicular to the Cu O2 planes is also discussed.