Magnetic Excitations in the Spin-Peierls System $CuGeO_3$

Abstract

We have calculated the magnetic excitation spectrum in frustrated and dimerized spin 1/2 Heisenberg chains for model parameters which describe the thermodynamics and low frequency spin dynamics in the spin--Peierls system $CuGeO_{3}$. As a test the chosen model is found to reproduce the lowest Raman excitation energy near $30 cm^{-1}$ in the dimerized phase. We establish the elementary triplet and singlet excitation branches below the continuum and estimate the interchain coupling effects on the dimerization parameter.

The postscript files of the figures are included (5 figures).The paper is submitted to Phys. Rev. letters