Spatially intertwined superconductivity and charge order in 1T-TaSSe revealed by scanning tunneling spectroscopy

TL;DR

This study uses high-resolution scanning tunneling spectroscopy to explore the spatial relationship between superconductivity and charge order in 1T-TaSSe, revealing a complex interplay with implications for quantum materials.

Contribution

It uncovers the spatial correlation between superconducting gap and charge order, demonstrating the link between charge order and superconductivity in 1T-TaSSe.

Findings

Superconducting gap varies smoothly over ~10 nm scale.

No correlation between SC gap and domain structure.

Significant correlation between SC gap and spectral weight of narrow band.

Abstract

The interplay of different emergent phenomena -- superconductivity (SC) and domain formation -- appearing on different spatial and energy scales are investigated using high-resolution scanning tunneling spectroscopy (STS) in the prototypical transition metal dichalcogenide superconductor $1T$-TaSSe single crystals ($T_{SC} = 3.2$ K) at temperatures from 1 to 20 K. Our major observation is that while the SC gap size smoothly varies on the scale of $\lesssim 10$ nm, its spatial distribution is not correlated to the domain structure. On the other hand, there is statistically significant correlation of the SC gap $\Delta_{SC}$ with spectral weight of the narrow band at the Fermi level formed from the same Ta $5d$ orbitals as the Mott-Hubbard band. We show that the narrow band follows the evolution of Hubbard bands in space, proving unambiguously its relation to the charge order. The correlations between the two suggest a non-trivial link between rapidly spatially varying charge order and superconductivity common in many quantum materials, and high-temperature superconductors in particular.