PCP1-5
On-site Coulomb energy in La2-xSrxCuO4 studied by resonant photoemission spectroscopy
13:30-15:00 Dec.3
*G. Kim1, M. Nagamoto1, T. Ishida1, N. Tsutsumi1, D. Ootsuki1, H. Kumigashira2, K. Ozawa3, M. Kitamura4, S. Komiya5, Y. Ando6, and T. Yoshida1
Graduate School of Human and Environmental Studies, Kyoto University, Sakyo-ku, Kyoto, Kyoto, 606-8501, Japan1
Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Aoba-ku, Sendai, Miyagi, 980-8577, Japan2
Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki, 305-0801, Japan3
Institute for Advanced Synchrotron Light Source, National Institutes for Quantum Science and Technology (QST), Aoba-ku, Sendai, Miyagi, 980-8579, Japan4
Materials Science Laboratory, Center Research Institute of Electric Power Industry, Nagasaka, Yokosuka, Kanagawa, 240-0196, Japan5
Physics Institute II, University of Cologne, Zülpicher Str. 77, 50937 Köln, Germany6
High-Tc superconductivity in cuprates is caused by carrier doping into a Mott insulator. It is important to reveal the nature of the strong on-site Coulomb interaction for understanding the electronic structure of high-Tc cuprates. Many studies have been conducted to experimentally determine the intra-atomic on-site Coulomb energy Udd (Upp) between Cu 3d electrons (O 2p electrons) [1-7]. Recently, the on-site Coulomb energies have been estimated using the Cini-Sawatzky method [8,9] for resonant photoemission spectra [6,7]. For single layer cuprates, the on-site Coulomb energy strongly depends on the presence or absence of apical oxygens for Cu sites [4,5]. Actually, the on-site Coulomb energy has been estimated to be Upp ~ 3.3 eV for T'-type Pr1.3-xLa0.7CexCuO4 without apical oxygens [7].
In this study, we have investigated the on-site Coulomb energies Udd and Upp for the single-layer T-type La2-xSrxCuO4 (x = 0.03, 0.15, and 0.22) by means of resonant photoemission spectroscopy. Figure 1 shows the valence-band spectra as a function of the incident photon energy for La2-xSrxCuO4 (x = 0.22). With increasing photon energy, the resonant structures shift toward higher binding energy as shown by bars in Fig. 1. These structures suggest the Auger two-hole satellite (O KVV auger structure). In order to estimate Upp, we have subtracted the spectrum at hn = 529.25 eV to that at hn = 526 eV and compared the subtracted spectrum with the O 2p valence-band spectrum at hn = 55 eV as shown in Fig. 2. Here, the contribution of the O 2p states was expected to be dominant in the spectrum at hn = 55 eV. Based on the Cini-Sawatzky method, we have conducted a numerical self-convolution for the O 2p one-hole spectrum at hn = 55 eV and obtained the two-hole spectrum. The energy difference between the Auger peak and the self-convoluted spectrum indicates Upp. Thus, Upp is estimated to be ~5.4 eV, which is in good agreement with Upp ~ 5 eV in the result of previous Auger spectroscopy measurement (x = 0.15) [1].
In this presentation, we will show the detail of the resonant photoemission spectra and the doping dependence of the on-site Coulomb energy for La2-xSrxCuO4.
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Keywords: resonant photoemission spectra, High-Tc superconductivity, cuprates, on-site Coulomb interaction, Mott insulator