Magnetic susceptibility of a CuO2 plane in the La2CuO4 system: I. RPA treatment of the Dzyaloshinskii-Moriya Interactions

TL;DR

This paper investigates the magnetic susceptibility of a CuO2 plane in La2CuO4, analyzing the effects of Dzyaloshinskii-Moriya interactions using RPA and spin-wave theories to understand anisotropies and quantum fluctuations.

Contribution

It introduces a comprehensive RPA treatment of Dzyaloshinskii-Moriya interactions in a 2D Heisenberg model relevant to La2CuO4, including susceptibility calculations across the transition.

Findings

Pronounced temperature-dependent anisotropies in susceptibility.

Evidence of strong quantum fluctuations near the N'eel temperature.

Spin-wave interactions significantly influence magnetic properties.

Abstract

Motivated by recent experiments on undoped La2CuO4, which found pronounced temperature-dependent anisotropies in the low-field magnetic susceptibility, we have investigated a two-dimensional square lattice of S=1/2 spins that interact via Heisenberg exchange plus the symmetric and anti-symmetric Dzyaloshinskii-Moriya anisotropies. We describe the transition to a state with long-ranged order, and find the spin-wave excitations, with a mean-field theory, linear spin-wave analysis, and using Tyablikov's RPA decoupling scheme. We find the different components of the susceptibility within all of these approximations, both below and above the N'eel temperature, and obtain evidence of strong quantum fluctuations and spin-wave interactions in a broad temperature region near the transition.