Abstract
Interplay among various collective electronic states such as charge density wave and superconductivity is of tremendous significance in low-dimensional electron systems. However, the atomistic and physical nature of the electronic structures underlying the interplay of exotic states, which is critical to clarifying its effect on remarkable properties of the electron systems, remains elusive, limiting our understanding of the superconducting mechanism. Here, we show evidence that an ordering of selenium and sulphur atoms surrounding tantalum within star-of-David clusters can boost superconductivity in a layered chalcogenide 1T-TaS2-xSex, which undergoes a superconducting transition in the nearly commensurate charge density wave phase. Advanced electron microscopy investigations reveal that such an ordered superstructure forms only in the x area, where the superconductivity manifests, and is destructible to the occurrence of the Mott metal-insulator transition. The present findings provide a novel dimension in understanding the relationship between lattice and electronic degrees of freedom.
Highlights
Interplay among various collective electronic states such as charge density wave and superconductivity is of tremendous significance in low-dimensional electron systems
The 12 electrons occupy the states below the distortion-induced gap and the thirteenth one dominates the states above the gap, resulting in a Mott insulating state that accounts for the high resistivity of the CCDW phase[14,15,16], (2) the neighbouring NCCDW phase contains the star-of-David clusters as well albeit that they are less homogeneously arranged[7], (3) with the rise of temperature, the Mott phase melts into the NCCDW phase with an extremely fast charge response and a sudden drop in resistivity, where several tens of stars organize into roughly hexagonal domains[10,17]
In the following, combining the Cs-corrected high-angle annular dark-field (HAADF)[30], annular bright-field (ABF)[31] scanning transmission electron microscopy (STEM) with electric transport measurements, we provide evidence that superconductivity in 1T-TaS2 À xSex (0rxr2.0) is characterized by an unexpected ordering of Se and S atoms within the star-ofDavid clusters
Summary
Interplay among various collective electronic states such as charge density wave and superconductivity is of tremendous significance in low-dimensional electron systems. In the following, combining the Cs-corrected high-angle annular dark-field (HAADF)[30], annular bright-field (ABF)[31] scanning transmission electron microscopy (STEM) with electric transport measurements, we provide evidence that superconductivity in 1T-TaS2 À xSex (0rxr2.0) is characterized by an unexpected ordering of Se and S atoms within the star-ofDavid clusters. Such an atomically ordered superstructure may account for the emergence of superconductivity, perhaps opening up yet another useful avenue in tailoring superconductivity or even Mott metal–insulator transition via the atomistic ordering/ disordering engineering
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