Wednesday, July 3, 2013

1307.0325 (Yuan Li et al.)

Doping-Dependent Raman Resonance in the Model High-Temperature
Superconductor HgBa2CuO4+d

Yuan Li, M. Le Tacon, Y. Matiks, A. V. Boris, T. Loew, C. T. Lin, Lu Chen, M. K. Chan, C. Dorow, L. Ji, N. Barisic, X. Zhao, M. Greven, B. Keimer
We study the model high-temperature superconductor HgBa2CuO4+d with electronic Raman scattering and optical ellipsometry over a wide doping range. The resonant Raman condition which enhances the scattering cross section of "two-magnon" excitations is found to change strongly with doping, and it corresponds to a rearrangement of inter-band optical transitions in the 1-3 eV range seen by ellipsometry. This unexpected change of the resonance condition allows us to reconcile the apparent discrepancy between Raman and x-ray detection of magnetic fluctuations in superconducting cuprates. Intriguingly, the strongest variation occurs across the doping level where the antinodal superconducting gap reaches its maximum.
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