Direct Evidence of Intrinsic Mott State and Its Layer-Parity Oscillation in a Breathing Kagome Crystal Down to Monolayer.

We report direct spectroscopic evidence of correlation-driven Mott states in layered Nb₃Cl₈ through combining scanning tunneling microscopy (STM) and dynamical mean-field theory. The Hubbard bands persist down to monolayer, providing the definitive evidence for the Mottness in Nb₃Cl₈. While the size of the Mott gap remains almost constant across all layers, a striking layer-parity-dependent oscillation emerges in the local density of states (LDOS) between even (n=2, 4, 6) and odd layers (n=1, 3, 5), which arises from the dimerization and correlation modulation of the obstructed atomic states, respectively. Our conclusions are supported by a critical technical advance in atomic-scale LDOS mapping for highly insulating systems. This Letter provides the definitive experimental verification of correlation-driven Mott ground states in Nb₃Cl₈, while establishing a general protocol for investigating the interplay of electronic correlation and interlayer coupling in layered insulators by using a low-temperature STM technique.