Rubidium-induced phase transitions among metallic, band-insulating, Mott-insulating phases in 1T -TaS₂

Realizing phase transitions via non-thermal sample manipulations is important not only for applications, but also for uncovering the underlying physics. Here, we report on the discovery of two distinct metal–insulator transitions in 1T-TaS₂ via angle-resolved photoemission spectroscopy and in-situ rubidium deposition. At 205 K, the rubidium deposition drives a normal metal–insulator transition via filling electrons into the conduction band. While at 225 K, however, the rubidium deposition drives a bandwidth-controlled Mott transition as characterized by a rapid collapsing of Mott gap and a loss of spectral weight of the lower Hubbard band. Our result, from a doping-controlled perspective, succeeds in distinguishing the metallic, band-insulating, and Mott-insulating phases of 1T-TaS₂, manifesting a delicate balance among the electron-itineracy, interlayer-coupling and Coulomb repulsion. We also establish an effective method to tune the balance between these interactions, which is useful in seeking exotic electronic phases and designing functional phase-changing devices.