Abstract
Utilizing resonant inelastic x-ray scattering, we report a previously unobserved mode in the excitation spectrum of and at 500 meV. The mode is peaked around the (, 0) point in reciprocal space and is observed to soften, and broaden, away from this point. Samples with , 0.01, 0.05, and 0.17 were studied. The new mode is found to be rapidly suppressed with increasing Sr content and is absent at , where it is replaced by a continuum of excitations. This mode is only observed when the incident x-ray polarization is normal to the CuO planes.
- Received 20 September 2007
DOI:https://doi.org/10.1103/PhysRevLett.100.097001
©2008 American Physical Society