Abstract
We consider the absorption of light with emission of one magnetic excitation in systems with a spin gap induced by quantum fluctuations. We argue that an electric-dipole transition is allowed on the condition that a virtual phonon instantaneously breaks the inversion symmetry. We derive an effective operator for the transition and argue that the proposed theory explains the polarized experiments in and .
- Received 21 October 2003
DOI:https://doi.org/10.1103/PhysRevB.70.024404
©2004 American Physical Society