Ishii K, Tsutsui K, Endoh Y, Tohyama T, Kuzushita K, Inami T, Ohwada K, Maekawa S, Masui T, Tajima S, Murakami Y, Mizuki J
Synchrotron Radiation Research Center, Japan Atomic Energy Research Institute, Hyogo 679-5148, Japan.
Phys Rev Lett. 2005 May 13;94(18):187002. doi: 10.1103/PhysRevLett.94.187002. Epub 2005 May 12.
Mott gap excitations in the optimally doped high-T(c) superconductor YBa(2)Cu(3)O(7-delta) (T(c)=93 K) have been studied by the resonant inelastic x-ray scattering method. Anisotropic spectra in the ab plane are observed in a twin-free crystal. The excitation from the one-dimensional CuO chain is enhanced at 2 eV near the zone boundary of the b* direction, while the excitation from the CuO2 plane is broad at 1.5-4 eV and almost independent of the momentum transfer. Theoretical calculations based on the one-dimensional and two-dimensional Hubbard model reproduces the observed spectra when different values of the on-site Coulomb energy are assumed. The Mott gap of the CuO chain site is found to be much smaller than that of the CuO2 plane site.
利用共振非弹性X射线散射方法研究了最佳掺杂的高温超导体YBa₂Cu₃O₇₋δ（Tc = 93 K）中的莫特能隙激发。在无孪晶的晶体中观察到ab平面内的各向异性光谱。来自一维CuO链的激发在b*方向的能带边界附近2 eV处增强，而来自CuO₂平面的激发在1.5 - 4 eV范围内较宽且几乎与动量转移无关。当假设在位库仑能有不同值时，基于一维和二维哈伯德模型的理论计算再现了观测到的光谱。发现CuO链位点的莫特能隙比CuO₂平面位点的小得多。
