Interlayer Charge Transfer Induced by Electronic Instabilities in the Natural van der Waals Heterostructure 4Hb−TaS2

The natural van der Waals heterostructure 4H_{b}-TaS_{2} composed of alternating 1T- and 1H-TaS_{2} layers serves as a platform for investigating the electronic correlations and layer-dependent properties of novel quantum materials. The temperature evolution of the conductivity spectra σ(ω) obtained through infrared spectroscopy elucidates the influence of band modifications associated with the charge-density-wave (CDW) superlattice on the 1T layer, resulting in a room-temperature energy gap, Δ_{CDW}≈0.35 eV. Supported by density functional theory calculations, we attribute the behavior of interband transitions to the convergence of the layers, which amplifies the charge transfer from the 1T to the 1H layers, progressing as the temperature decreases. This phenomenon leads to an enhanced carrier density. The presence of an energy gap and the temperature-tunable charge transfer within the bulk of 4H_{b}-TaS_{2}-driven by layer-dependent CDW states-contribute to a more comprehensive understanding of other complex compounds of transition-metal dichalcogenides.