The discovery of higher-temperature superconductivity in FeSe monolayers on ${\mathrm{SrTiO}}_3$ substrates has sparked a surge of interest in the interface superconductivity. One point of agreement reached to date is that modulation doping by impurities in the substrate is critical for the enhanced superconductivity. Remarkably, the universal doping about 0.1 electrons per Fe, i.e., so-called “magic” doping, has been observed on a range of Ti oxide substrates, which concludes that there likely is some important interaction limiting the FeSe doping. Our study discovers that the polarization change at the interface Se because of the close proximity to the substrate from that in the free-standing FeSe film significantly amplifies the total potential difference at the interface above and beyond the work function difference for charge transfer. Additionally, the titanate substrate with a large number of free electrons basically serves as an “infinite” charge reservoir, which leads to the saturated FeSe doping with the complete removal of the interface potential gradient. Our work has developed the theory for modulation doping in the van der Waals materials/oxides heterostructure, providing a solution to the puzzle of magic doping in FeSe monolayers on titanates. The information also presents experimental pathways to accommodate a variable carrier density of FeSe monolayers via modulation doping.

中文翻译：

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FeSe 单层在 SrTiO3 上的调制掺杂

FeSe单层中高温超导性的发现${\mathrm{氧化锶}}_3$基板引发了对界面超导性的浓厚兴趣。迄今为止达成的一个共识是，衬底中杂质的调制掺杂对于增强的超导性至关重要。值得注意的是，已经在一系列氧化钛衬底上观察到每个 Fe 大约 0.1 个电子的普遍掺杂，即所谓的“神奇”掺杂，这表明可能存在一些限制 FeSe 掺杂的重要相互作用。我们的研究发现，由于与自支撑 FeSe 薄膜中的衬底非常接近，界面 Se 处的极化变化显着放大了界面处的总电位差，超过了电荷转移的功函数差。此外，具有大量自由电子的钛酸盐衬底基本上充当“无限”电荷库，这导致饱和FeSe掺杂完全消除了界面电位梯度。我们的工作发展了范德华材料/氧化物异质结构中调制掺杂的理论，为钛酸盐上的 FeSe 单分子层中的魔法掺杂难题提供了解决方案。该信息还提供了通过调制掺杂来适应 FeSe 单层的可变载流子密度的实验途径。为钛酸盐上的 FeSe 单分子层中的魔法掺杂难题提供了解决方案。该信息还提供了通过调制掺杂来适应 FeSe 单层的可变载流子密度的实验途径。为钛酸盐上的 FeSe 单分子层中的魔法掺杂难题提供了解决方案。该信息还提供了通过调制掺杂来适应 FeSe 单层的可变载流子密度的实验途径。