LAUSR

Tuning the electronic properties of a matter is of fundamental interest in scientific research as well as in applications. Recently, the Mott insulator-metal transition has been reported in a pristine layered transition metal dichalcogenide 1T-TaS$${}_{2}$$2, with the transition triggered by an optical excitation, a gate controlled intercalation, or a voltage pulse. However, the sudden insulator-metal transition hinders an exploration of how the transition evolves. Here, we report the strain as a possible new tuning parameter to induce Mott gap collapse in 1T-TaS$${}_{2}$$2. In a strain-rich area, we find a mosaic state with distinct electronic density of states within different domains. In a corrugated surface, we further observe and analyze a smooth evolution from a Mott gap state to a metallic state. Our results shed new lights on the understanding of the insulator-metal transition and promote a controllable strain engineering on the design of switching devices in the future.Mott insulation and charge density waves are fascinating phenomena which alter the electronic structure of a system and occur via the complex interplay of a number of different parameters. Here, the authors use scanning tunnelling microscopy to investigate the localised changes in the electronic state near the insulator-metal transition of 1T-TaS2 and find that strain may play a role.