Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany.
Phys Rev Lett. 2009 Oct 30;103(18):187401. doi: 10.1103/PhysRevLett.103.187401. Epub 2009 Oct 27.
Spectroscopic ellipsometry was used to study the dielectric function of LiCuVO4, a compound comprised of chains of edge-sharing CuO4 plaquettes, in the spectral range 0.75-6.5 eV at temperatures 7-300 K. For photon polarization along the chains, the data reveal a weak but well-resolved two-peak structure centered at 2.15 and 2.95 eV whose spectral weight is strongly enhanced upon cooling near the magnetic ordering temperature. We identify these features as an exciton doublet in the Mott-Hubbard gap that emerges as a consequence of the Coulomb interaction between electrons on nearest and next-nearest-neighbor sites along the chains. Our results and methodology can be used to address the role of the long-range Coulomb repulsion for compounds with doped copper-oxide chains and planes.
光谱椭圆偏振法被用于研究 LiCuVO4 的介电函数，LiCuVO4 是由边缘共享的 CuO4 平面链组成的化合物，光谱范围为 0.75-6.5eV，温度范围为 7-300K。对于沿着链的光子偏振，数据显示出一个微弱但分辨率很好的双峰结构，中心位于 2.15 和 2.95eV，其光谱权重在接近磁有序温度时强烈增强。我们将这些特征识别为莫特-哈伯德带隙中的激子双峰，这是由于链上最近邻和次近邻位置上电子之间的库仑相互作用而出现的。我们的结果和方法可用于解决具有掺杂铜氧化物链和平面的化合物中长程库仑排斥的作用。
