Tantalum disulfide (1T-TaS₂) is a quasi-two-dimensional transition metal dichalcogenide (TMD) that exhibits a series of charge density wave (CDW) transitions upon cooling and heating. These collective electronic phases can be tuned or disrupted by external stimuli such as pressure, electric fields, or illumination, leading to metastable or hidden metallic states. In nanoscale crystals of 1T-TaS₂, rapid cooling suppresses the insulating commensurate CDW (CCDW) phase and stabilizes a metastable metallic state, known as the super-cooled nearly commensurate CDW (SC-NCCDW) phase. However, the atomic-scale structure and microscopic origin of this state remain elusive. Here, we combine electrical transport measurements with structural characterization to elucidate the nature of the SC-NCCDW phase in 1T-TaS₂ nanocrystals. Temperature-dependent X-ray diffraction reveals that, under gradual cooling, the NCCDW-to-CCDW transition is accompanied by lattice-volume expansion. In contrast, this anomaly is strongly suppressed upon rapid cooling, correlating with the stabilization of the SC-NCCDW state. Complementary high-resolution transmission electron microscopy (HR-TEM) shows that rapid cooling produces a mixed-phase configuration containing structural motifs of both NCCDW and CCDW phases, indicating that the SC-NCCDW represents an intermediate structural configuration frozen by kinetic constraints. These findings provide, to our knowledge, the first direct structural evidence of the SC-NCCDW state and offer a mechanistic understanding of cooling-rate-controlled metastability in layered correlated compounds such as 1T-TaS₂.

In this work, we present a theoretical investigation of electron–surface optical phonon (SOP) interactions and Auger recombination processes in monolayer PtSe2 and PtS2 supported on polar dielectric substrates such as SiO2 and hBN. The analysis is based on a low-energy effective Hamiltonian describing the electronic structure near the K and K′ valleys of the Brillouin zone, combined with the Fröhlich interaction model to account for the coupling between charge carriers and substrate-induced optical phonons. The comparison between Auger recombination and SOP scattering is performed at a representative carrier density of n=1012 cm−2 within the investigated temperature range. We analyze the formation of polaronic states arising from the hybridization between electronic excitations and SOPs and evaluate the associated Rabi splitting energies and oscillator strengths. The temperature dependence of the SOP-induced scattering rates and the influence of the monolayer–substrate separation on carrier–phonon interactions are also examined. Our results show that electron–phonon coupling strongly depends on the dielectric properties of the supporting substrate, with larger anticrossing gaps predicted for hBN-supported structures compared with SiO2-supported systems. Auger recombination constitutes the dominant carrier relaxation channel within the investigated temperature range, whereas SOP scattering becomes increasingly significant at elevated temperatures, where both mechanisms approach a comparable inelastic phonon-limited regime. These findings highlight the role of dielectric engineering in controlling carrier relaxation dynamics in Pt-based TMDC heterostructures.