Re-emergence of superconductivity via pressure-induced Lifshitz transition in preserved 6R-TaS2 crystal structure

Investigating the implications of interlayer coupling on superconductivity is vital for comprehending the intrinsic mechanisms of two-dimensional materials. Van der Waals heterojunctions have attracted extensive research owing to their exotic interlayer coupling. In this study, we investigated the natural heterostructure superconductor featuring 6R-TaS₂ via measurements of electrical resistance, the Hall effect, and in-situ synchrotron X-ray diffraction (XRD) under various pressures. The study findings show that the superconducting transition temperature (T_c) of 6R-TaS₂ in the range of 0–32.5 GPa exhibits an unusual double-dome behavior as a function of pressure, with the first and second domes in the pressure range of 0–5.3 and 6.8–32.5 GPa, respectively. At 56.6 GPa, a new superconducting phase with a T_c of 2 K was observed. The XRD results show that the singular evolution of the T_c is independent of the structural phase transition. Combining the XRD results, first-principles calculations, and Hall effect measurements, we found that different interlayer coupling effects resulted in double dome superconductivity and the re-emergence of superconducting. Our findings shed light on the pivotal role of interlayer coupling in driving the anomalous alterations in superconducting properties triggered by charge transfer and Fermi surface reconstruction and provide an alternative route for comprehending the mechanisms of superconductivity in transition metal dichalcogenides (TMDs).