Suppression of structural and magnetic phase transitions in layered exfoliated kagome semiconductor Nb₃Cl₈

Kagome materials with flat bands provide ideal platforms for engineering correlated quantum states. Establishing unambiguous phase identification and achieving effective control over phase transitions are essential for manipulating these exotic quantum states. Here, we report the suppression of structural and magnetic phase transitions in exfoliated Nb₃Cl₈ nanoflakes, a van der Waals breathing kagome semiconductor. Through temperature-dependent Raman spectroscopy, we identify four diagnostic phonon modes that abruptly shift at the bulk α - β phase transition with 40 K hysteresis, characteristic of first-order behavior. Interestingly, exfoliated nanoflakes (thickness < 100 nm) retain the high-temperature α-phase down to 2 K, evidenced by the minimal temperature dependence of phonon frequencies and persistent quasi-elastic scattering signals, indicative of spin-energy fluctuations. Our study bridges a critical gap between interlayer coupling and phase transitions of van der Waals kagome compounds, opening new pathways for manipulating and designing novel correlated quantum phases.