Multiple pre-edge structures in Cu K-edge x-ray absorption spectra of high-T-c cuprates revealed by high-resolution x-ray absorption spectroscopy

作者：Gougoussis C^*; Rueff J P; Calandra M; d'Astuto M; Jarrige I; Ishii H; Shukla A; Yamada I; Azuma M; Takano M

来源：Physical Review B, 2010, 81(22): 224519.

DOI：10.1103/PhysRevB.81.224519

Using high-resolution x-ray absorption spectroscopy and state-of-the-art electronic structure calculations we demonstrate that the pre-edge region at the Cu K edge of high-T-c cuprates is composed of several excitations invisible in standard x-ray absorption spectra. We consider in detail the case of Ca2-xCuO2Cl2 and show that the many pre-edge excitations (two for c-axis polarization, four for in-plane polarization and out-of-plane incident x-ray momentum) are dominated by off-site transitions and intersite hybridization. This demonstrates the relevance of approaches beyond the single-site model for the description of the pre edges of correlated materials. Finally, we show the occurrence of a doubling of the main edge peak that is most visible when the polarization is along the c axis. This doubling, that has not been seen in any previous absorption data in cuprates, is not reproduced by first-principles calculations. We suggest that this peak is due to many-body charge-transfer excitations while all the other visible far-edge structures are single particle in origin. Our work indicates that previous interpretations of the Cu K-edge x-ray absorption spectra in high-T-c cuprates can be profitably reconsidered.

• 出版日期2010-6-24