Noncentrosymmetric Mott ground state in the breathing kagome lattice
Phys. Rev. B 112, 214116 – Published 26 December, 2025
DOI: https://doi.org/10.1103/9n97-dp2z
Abstract
The breathing Kagome material has recently been identified as a single-band Mott insulator and theoretically predicted to host coexisting ferroelectricity, magnetism, and ferrovalley—yet experimental verification of these predictions remains lacking. Here, through polarization- and temperature-dependent Raman and second harmonic generation measurements, we reveal that the low-temperature (LT) phase of this material retains rotational symmetry while breaking inversion symmetry. We propose that the structural phase transition at corresponds to a stacking-order transition: from centrosymmetric AB stacking to noncentrosymmetric AA/BB stacking, driven by enhanced interlayer electric dipole-dipole interactions. With an AA/BB stacking sequence, the LT phase exhibits net electric dipole moments oriented perpendicular to the kagome plane. Our findings provide directly experimental evidence for the existence of a noncentrosymmetric Mott ground state, thereby establishing a unique platform for investigating the interplay between inversion symmetry breaking and strong electron correlation.
