Pressure induced nonmonotonic evolution of superconductivity in 6R-TaS2 with a natural bulk van der Waals heterostructure

TL;DR

This study investigates how pressure affects superconductivity and charge-density-wave order in 6R-TaS2, revealing a nonmonotonic evolution linked to the material's layered structure and Josephson junction behavior.

Contribution

It demonstrates the pressure-induced nonmonotonic evolution of superconductivity and CDW in 6R-TaS2, highlighting the role of Josephson coupling and emergent superconductivity after CDW suppression.

Findings

Superconductivity exhibits a dome-shaped dependence on pressure.

Complete collapse of CDW occurs at a critical pressure around 2.9 GPa.

Superconductivity re-emerges above the critical pressure, indicating complex electronic interactions.

Abstract

The natural bulk van der Waals heterostructures compound 6R-TaS2 consists of alternate stacking 1T- and 1H-TaS2 monolayers, creating a unique system that incorporates charge-density-wave (CDW) order and superconductivity (SC) in distinct monolayers. Here, after confirming that the 2D nature of the lattice is preserved up to 8 GPa in 6R-TaS2, we documented an unusual evolution of CDW and SC by conducting highpressure electronic transport measurements. Upon compression, we observe a gradual suppression of CDW within the 1T-layers, while the SC exhibits a dome-shaped behavior that terminates at a critical pressure Pc around 2.9 GPa. By taking account of the fact that the substantial suppression of SC is concomitant with the complete collapse of CDW order at Pc, we argue that the 6R-TaS2 behaves like a stack of Josephson junctions and thus the suppressed superconductivity can be attributed to the weakening of Josephson coupling associated with the presence of CDW fluctuations in the 1T-layers. Furthermore, the SC reversely enhances above Pc, implying the development of emergent superconductivity in the 1T-layers after the melting of T-layer CDW orders. These results show that the 6R-TaS2 not only provides a promising platform to explore emergent phenomena but also serves as a model system to study the complex interactions between competing electronic states.