Recently, a research group from Prof. YANG Zhaorong from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences, together with researchers from Nanjing University and Anhui University, discovered the pressure-induced unusual evolution of superconductivity (SC) and exotic interplay between SC and charge-density-wave (CDW) order in natural bulk van der Waals heterostructure, by combining the comprehensive high-pressure measurements and first-principles calculations.
The research results were published in Physical Review Letters.
Engineering van der Waals heterostructures (vdWHs) via pressure in a continuous manner not only allows for generation of new states of matter, but also provides a distinctive platform to study the interplay between competing electronic orders in separated layers. Natural bulk vdWHs 6R-TaS2 incorporates CDW order and SC in distinct 1T- and 1H-TaS2 monolayers and is equivalent to a stack of superconductor-insulator-superconductor Josephson junctions.
In this study, researchers studied the pressure tuning of the interplay between SC and CDW order in 6R-TaS2. By compressing 6R-TaS2, they showed that the superconducting Tc exhibits a nonmonotonic behavior: initial increases, then plateaus, then depresses, and finally resurges at higher pressures. Detailed analyses indicated that the nonmonotonic behavior can be accounted for in a scenario of pressure-tuned Josephson coupling associated with the evolving of the 1T-layer: first from insulator to metal both with static CDW order, then to metal with fluctuating CDW order, followed by finally becoming superconducting.
“Our findings not only revealed the novel physical properties of vdWHs materials at high pressures, but also provided a new perspective for understanding superconductivity in complex quantum materials, which is of great significance for quantum material design and applications.” said Prof. YANG Zhaorong.
Figure. Schematic diagram of pressure-tuned Josephson coupling in 6R-TaS2. (Image by ZHOU Yonghui)
