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| 21世紀COEセミナー「Probing Gaps and Pseudogaps in Cuprates by Infrared Spectroscopy」 |
| 日時 |
平成１８年（２００６年）１１月２２日（水）１０：３０〜１２：００ |
| 場所 |
中セミナー室（H601） |
| 講師 |
Nicole Bontemps 教授 (CNRS (UPR5) - ESPCI)
現 東京大学大学院 新領域創成科学研究科 客員教授 |
| 題目 |
Probing Gaps and Pseudogaps in Cuprates by Infrared Spectroscopy |
| 概要 |
Identifying how remote high critical temperature superconductors are from conventional metals is an important clue for these materials. Infrared spectroscopy can provide a model independent insight about the properties of these “strange metals”. Indeed the optical conductivity integrated up to a set of cut-off frequencies (spectral weight) has clear signatures when studied versus temperature and cut-off frequency, for a metal (full Fermi surface) or a partially gapped state.
We will first present our data deduced from in-plane reflectivity measurements, in electron doped cuprates (Pr2-xCexCuO4, x = 0.11, 0.13, 0.15, 0.17). There, we find a clear spectroscopic signature of the onset of a pseudogap up to x = 0.15. Recent infrared results in a reduced (superconducting) sample and an oxidized non superconducting sample for x = 0.17, together with inelastic neutron scattering data, point towards a magnetic origin of the pseudogap. In contrast, in hole doped materials (two layers cuprate Bi2Sr2CaCuO8+δ), the pseudogap is hardly seen in the in-plane conductivity. This may imply that the pseudogap in electron doped and hole doped compounds has a different origin. |
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