论文标题
负电荷转移绝缘子中的孔掺杂
Hole doping in a negative charge transfer insulator
论文作者
论文摘要
$ re $ nio $ _3 $是一个负电荷转移能源系统，并表现出温度驱动的金属 - 绝缘体过渡（MIT），也伴随着债券相比（BD）过渡。为了探索孔掺杂如何影响BD过渡，我们研究了ND $ _ {1-x} $ _x $ _X $ _x $ nio $ _3 $的单晶薄膜的电子结构，该薄膜是基于Synchrotron的实验和{\ IT {\ IT ab-initio}计算的。对于$ x $的小价值，我们发现掺杂的孔位于掺杂剂Ca $^{2+} $ ions周围的一个或多个NI站点上，而其余晶格的BD状态仍然完好无损。有效的电荷转移能（$δ$）随着CA浓度的增加而增加，而BD相的形成不超过关键$ x $，从而抑制了绝缘阶段。我们目前的研究牢固地表明，BD模式的外观对于麻省理工学院至关重要，并就结构性扭曲在$ re $ $ $ nio $ _3 $系列中的结构扭曲作用进行了长期辩论。
$RE$NiO$_3$ is a negative charge transfer energy system and exhibits a temperature-driven metal-insulator transition (MIT), which is also accompanied by a bond disproportionation (BD) transition. In order to explore how hole doping affects the BD transition, we have investigated the electronic structure of single-crystalline thin films of Nd$_{1-x}$Ca$_x$NiO$_3$ by synchrotron based experiments and {\it ab-initio} calculations. For a small value of $x$, we find that the doped holes are localized on one or more Ni sites around the dopant Ca$^{2+}$ ions, while the BD state for the rest of the lattice remains intact. The effective charge transfer energy ($Δ$) increases with Ca concentration and the formation of BD phase is not favored above a critical $x$, suppressing the insulating phase. Our present study firmly demonstrates that the appearance of BD mode is essential for the MIT and settles a long-standing debate about the role of structural distortions for the MIT of the $RE$NiO$_3$ series.
