THE SPIN-PEIERLS TRANSITION BEYOND THE ADIABATIC APPROXIMATION

A. O. DOBRY; D. C. CABRA; G. L. ROSSINI

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

American Physical Society

Lugar: New York; Año: 2007 vol. 75 p. 45122 - 45131

0163-1829

We develop a theory of the spin-Peierls transition taking into account the three dimensional character of the phonon field. Our approach does not rely on the adiabatic or mean field treatment for the phonons. It is instead based in the exact integration of the phonon field, the exact long wavelength solution of the one chain spin problem, and then a mean field approximation for the interchain interaction. We show that the spin gap and the critical temperature are strongly reduced due to the finite frequency effects of the phonon coupling transverse to the magnetic chains. We show that the long standing discussion on absence of a soft mode in this compound can be naturally resolved within our theory. We claim that our results should be applicable to the inorganic spin-Peierls compound CuGeO_3.