TEMPERATURE-DEPENDENCE OF THE RAMAN-SCATTERING IN THE 2-DIMENSIONAL HEISENBERG-ANTIFERROMAGNET

We have analyzed the B(lg) finite-temperature Raman response of the antiferromagnetic Heisenberg model. For temperatures in the range of the experimental data obtained for La2CuO4, i.e., between T = 0 and a little higher than the Neel transition temperature T(N), we obtain a qualitatively good agreement with experimental measurements: the two-magnon energy is almost independent of the temperature, and its intensity decreases by approximately 20% when T is increased from 0 to T greater-than-or-equal-to T(N). For temperatures T approximately (2-4)T(N) corresponding in the undoped compound La2CuO4 to the paramagnetic phase, the two-magnon peak is still recognizable, showing the nonsensitivity of the short-wavelength spin waves to the presence or absence of long-range magnetic order.