Local gate control of Mott metal-insulator transition in a 2D metal-organic framework

TL;DR

This study demonstrates local gate control of Mott metal-insulator transitions in a 2D kagome metal-organic framework, revealing the potential for electrostatically tuning many-body quantum phases in 2D materials.

Contribution

It reports the first experimental realization of a Mott insulator in a 2D kagome MOF and shows local electrostatic control of its electronic phase transition.

Findings

Identified a ~200 meV energy gap consistent with Mott insulating behavior.

Achieved local tuning of the electron population and induced MITs via gating.

Confirmed the Mott insulator state with STM and spectroscopy measurements.

Abstract

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.