Lowe Benjamin, Field Bernard, Hellerstedt Jack, Ceddia Julian, Nourse Henry L, Powell Ben J, Medhekar Nikhil V, Schiffrin Agustin
School of Physics and Astronomy, Monash University, Clayton, VIC, Australia.
ARC Centre of Excellence in Future Low-Energy Electronics Technologies, Monash University, Clayton, VIC, Australia.
Nat Commun. 2024 Apr 26;15(1):3559. doi: 10.1038/s41467-024-47766-8.
Electron-electron interactions in materials lead to exotic many-body quantum phenomena, including Mott metal-insulator transitions (MITs), magnetism, quantum spin liquids, and superconductivity. These phases depend on electronic band occupation and can be controlled via the chemical potential. Flat bands in two-dimensional (2D) and layered materials with a kagome lattice enhance electronic correlations. Although theoretically predicted, correlated-electron Mott insulating phases in monolayer 2D metal-organic frameworks (MOFs) with a kagome structure have not yet been realised experimentally. Here, we synthesise a 2D kagome MOF on a 2D insulator. Scanning tunnelling microscopy (STM) and spectroscopy reveal a MOF electronic energy gap of ∼200 meV, consistent with dynamical mean-field theory predictions of a Mott insulator. Combining template-induced (via work function variations of the substrate) and STM probe-induced gating, we locally tune the electron population of the MOF kagome bands and induce Mott MITs. These findings enable technologies based on electrostatic control of many-body quantum phases in 2D MOFs.
材料中的电子-电子相互作用会导致奇异的多体量子现象，包括莫特金属-绝缘体转变（MITs）、磁性、量子自旋液体和超导性。这些相取决于电子能带占据情况，并且可以通过化学势来控制。具有 kagome 晶格的二维（2D）和层状材料中的平带会增强电子相关性。尽管有理论预测，但具有 kagome 结构的单层二维金属有机框架（MOF）中的关联电子莫特绝缘相尚未通过实验实现。在这里，我们在二维绝缘体上合成了一种二维 kagome MOF。扫描隧道显微镜（STM）和光谱学揭示了约 200 meV 的 MOF 电子能隙，这与莫特绝缘体的动态平均场理论预测一致。结合模板诱导（通过衬底的功函数变化）和 STM 探针诱导的门控，我们局部调节了 MOF kagome 带的电子填充并诱导了莫特 MITs。这些发现推动了基于二维 MOF 中多体量子相静电控制的技术发展。
