Superconducting dome by tuning through a Van Hove singularity in a two-dimensional metal

Abstract

Chemical substitution is a promising route for the exploration of a rich variety of doping- and/or disorder-dependent collective phenomena in low-dimensional quantum materials. Here we show that transition metal dichalcogenide alloys are ideal platforms to this purpose. In particular, we demonstrate the emergence of superconductivity in the otherwise metallic single-layer TaSe${}_2$ by minute electron doping provided by substitutional W atoms. We investigate the temperature- and magnetic field-dependence of the superconducting state of Ta${}_{1-\delta }$W${}_{\delta }$Se${}_2$ with electron doping ($\delta$) using variable temperature (0.34 K - 4.2 K) scanning tunneling spectroscopy (STS). We unveil the emergence of a superconducting dome spanning 0.003 < $\delta$ < 0.03 with a maximized critical temperature of 0.9 K, a significant increase from that of bulk TaSe${}_2$ (T${}_C$ = 0.14 K). Superconductivity emerges from an increase of the density of states (DOS) as the Fermi surface approaches a van Hove singularity due to doping. Once the singularity is reached, however, the DOS decreases with $\delta$, which gradually weakens the superconducting state, thus shaping the superconducting dome. Lastly, our doping-dependent measurements allow us to unambiguously track the development of a Coulomb glass phase triggered by disorder due to W dopants.

This is the pre-peer reviewed version of an article that has been published in final form at npj 2D materials and applications [https://doi.org/10.1038/s41699-023-00401-4]

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• Controlling many-body states by the electric-field effect in a two-dimensional material
• Unexpected two-fold symmetric superconductivity in few-layer NbSe${}_2$
• Observation of superconducting collective modes from competing pairing instabilities in single-layer NbSe${}_2$
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Cited by in corpus (1)

• Controlling charge density order in 2H-TaSe${}_2$ using a van Hove singularity