Scanning tunnelling microscopy and spectroscopy investigation of rubidium-induced Mott–Hubbard transition on 1T–TaS2

The influence of rubidium deposition on structural and electronic properties of 1T–TaS₂ was investigated by scanning tunnelling microscopy and spectroscopy at room temperature. The hexagonally ordered charge density wave (CDW) of the clean surface exhibits a rectangular symmetry upon rubidium adsorption. The spectroscopy data signals a Mott–Hubbard phase transition by an energy gap between upper and lower Hubbard bands giving rise to a Coulomb interaction energy of 1 eV. Owing to spatially resolved spectroscopy the energy gap can be directly related to the rectangular CDW phase. In addition, rubidium adsorption leads to the formation of a network of linear wires. Scanning tunnelling spectroscopy indicates that the wires are most likely not fabricated from rubidium.