Numerical Calculations of the B1g Raman Spectrum of the Two-Dimensional Heisenberg Model

Details Numerical Calculations of the B1g Raman Spectrum of the Two-Dimensional Heisenberg Model Numerical Calculations of the B1g Raman Spectrum of the Two-Dimensional Heisenberg Model

1997-11-10

arxiv.org/abs/cond-mat/9711083v1

Phys. Rev B 57, 8478 (1998)

Physics

Condensed Matter

Strongly Correlated Electrons

15 pages, Revtex, 13 PostScript figures

Scientific paper

10.1103/PhysRevB.57.8478

The B1g Raman spectrum of the two-dimensional S=1/2 Heisenberg model is discussed within Loudon-Fleury theory at both zero and finite temperature. The exact T=0 spectrum for lattices with up to 6*6 sites is computed using Lanczos exact diagonalization. A quantum Monte Carlo (QMC) method is used to calculate the corresponding imaginary-time correlation function and its first two derivatives for lattices with up to 16*16 spins. The imaginary-time data is continued to real frequency using the maximum-entropy method, as well as a fit based on spinwave theory. The numerical results are compared with spinwave calculations for finite lattices. There is a surprisingly large change in the exact spectrum going from 4*4 to 6*6 sites. In the former case there is a single dominant two-magnon peak at frequency w/J appr. 3.0, whereas in the latter case there are two approximately equal-sized peaks at w/J appr. 2.7 and 3.9. This is in good qualitative agreement with the spinwave calculations including two-magnon processes on the same lattices. Both the Lanczos and the QMC results indicate that the actual infinite-size two-magnon profile is broader than the narrow peak obtained in spinwave theory, but the positions of the maxima agree to within a few percent. The higher-order contributions present in the numerical results are merged with the two-magnon profile and extend up to frequencies w/J appr. 7. The first three frequency cumulants of the spectrum are in excellent agreement with results previously obtained from a series expansion around the Ising limit. Typical experimental B1g$ spectra for La2CuO4 are only slightly broader than what we obtain here. The exchange constant extracted from the peak position is J appr. 1400K, in good agreement with values obtained from neutron scattering and NMR experiments.

Affiliated with

Also associated with

No associations

Rating

Numerical Calculations of the B1g Raman Spectrum of the Two-Dimensional Heisenberg Model does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Numerical Calculations of the B1g Raman Spectrum of the Two-Dimensional Heisenberg Model, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Numerical Calculations of the B1g Raman Spectrum of the Two-Dimensional Heisenberg Model will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-200903