Visualizing Spatial Evolution of Electron-Correlated Interface in Two-Dimensional Heterostructures

Area of Science:

• Condensed Matter Physics
• Materials Science
• Surface Science

Background:

• Understanding interfacial electronic structures is crucial for electron-correlated materials.
• Phase engineering offers a pathway to tune material properties.

Purpose of the Study:

• To microscopically visualize the evolution of electronic structures at the interface of a phase-engineered monolayer NbSe2 heterostructure.
• To investigate the interplay between metallic and Mott insulating states at the H/T phase boundary.
• To elucidate the mechanism behind Mott gap collapse at the electronic phase transition.

Main Methods:

• Scanning tunneling microscopy (STM) for high-resolution imaging.
• Scanning tunneling spectroscopy (STS) for electronic structure analysis.
• Theoretical calculations to support experimental observations.

Main Results:

• The metallic H-NbSe2 state penetrates the Mott insulating T-NbSe2 at the interface.
• A significant 2D charge density wave (CDW) proximity effect is observed.
• Mott gap collapse and disappearance of the upper Hubbard band occur at the transition region.
• Theoretical calculations attribute Mott gap collapse to interface-induced electron doping.

Conclusions:

• Phase engineering provides a method to control Mott insulating states in electron-correlated systems.
• The study offers a microscopical understanding of interactions between different electron-correlated domains.
• Interface-induced electron doping is key to understanding Mott gap collapse.