Unveiling the landscape of Mottness and its proximity to superconductivity in 4Hb-TaS2

Mott physics lies at the heart of many intriguing quantum phenomena. Recently, van der Waals materials emerge as a powerful platform to explore these correlated electronic states, yet tracking how such a Mott state develops and interacts with neighboring phases remains an experimental challenge. Here we use scanning tunnelling spectroscopy to study a filling-controlled Mott state and its interplay with superconductivity in 4Hb-TaS2, which interleaves strongly correlated 1T-TaS2 layers and superconducting 1H-TaS2 layers. By resolving the electronic spectral function across different filling levels driven by interlayer charge transfer, we quantitatively capture the continuous evolution of the Mott state, characterized by the emergence of Mott-Hubbard bands and the systematic suppression of the central quasiparticle peak. Moreover, while the 1H layers exhibit a uniform, fully opened superconducting gap, the heavily correlated electrons in the 1T layers act destructively against pairing, creating nanoscale, non-superconducting paramagnetic puddles. Our findings provide a quintessential visualization of the iconic Hubbard model and establish layered heterostructures as an ideal playground for designing exotic correlated quantum phases. 4Hb-TaS2 is composed of alternating strongly correlated 1T-TaS2 layers and superconducting 1H-TaS2 layers. Here, the authors demonstrate that the 1T-TaS2 layer is near the border of the Mott criterion and exhibits non-superconducting, paramagnetic puddles at the nanoscale.