We investigate the variation of charge dynamics in the course of the filling-control metal-insulator transitions (MITs) for pyrochlore ($R$ being rare-earth ions). With widely changing of $R$ ions from Lu to Pr, the antiferromagnetic transition temperature systematically increases while the magnitude of the charge gap decreases toward zero at the hypothetical bandwidth-control Mott transition. It is attributable to the reduction of effective electron correlation in the Mott-Hubbard insulator regime. Doping holes gives rise to the filling-control MITs from antiferromagnetic insulators to paramagnetic metals accompanied by the collapse of the Mott-Hubbard gaps. The doping-induced spectral weight transfer of the optical conductivity from the above-gap region to the in-gap region is nearly proportional to the doping level, whose rate is enhanced with the reduction of the electron correlation, in accord with the standard Mott criticality.

中文翻译：

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高度相关的烧绿石酸钌酸盐中的Mott-Hubbard缺口及其掺杂引起的塌陷

我们研究了烧绿石的填充控制金属-绝缘体转变（MITs）过程中电荷动力学的变化（$\mathrm{[R}$是稀土离子）。随着广泛的变化$\mathrm{[R}$从Lu到Pr离子，在假定的带宽控制Mott跃迁下，反铁磁跃迁温度系统地增加，而电荷隙的大小则朝零减小。这归因于莫特-哈伯德绝缘子体系中有效电子相关性的降低。掺杂孔引起了从反铁磁绝缘体到顺磁性金属的填充控制MIT，并伴随着Mott-Hubbard间隙的塌陷。掺杂引起的光导率从间隙上方区域到间隙内区域的光谱重量转移几乎与掺杂水平成正比，符合标准Mott临界度，掺杂水平随电子相关性的降低而提高。 。