First-principles studies on superconductivity in quintuple-layer M2X3 (M=Nb, Ta; X=S, Se)

Abstract

Transition metal dichalcogenides have attracted significant interest due to their rich physi cal properties, including charge density waves and superconductivity. They feature a characteristic sandwich structure, with a transition metal layer between two chalcogen layers. Recently, a quintuple-layer material, Nb2S3, was successfully synthesized, consisting of two Nb layers sandwiched between three S layers. In this study, we use first-principles calculations to investigate the electron-phonon coupling (EPC) and superconducting properties of the quintuple-layer M2X3 (M = Nb and Ta; X = S and Se). Our results show that all four M2X3 monolayers are dynamically and thermally stable, exhibiting no imaginary modes in their phonon dispersions. They also display semimetallic electronic band structures with small Fermi surfaces around the Γ and K points. EPC calculations reveal that the superconductivity transition temperatures (Tc) are 4.4, 2.0, 2.4, and 0.1 K for Nb2S3, Nb2Se3, Ta2S3, and Ta2Se3, respectively. These values are approximately inversely proportional to the relative atomic masses of the constituent elements, a trend also observed in MX2 (M = Nb and Ta; X = S and Se). Furthermore, we propose that the Tc can be enhanced by slightly shifting the Fermi energy to the van Hove singularity. This work provides an effective strategy for tailoring the physical properties of the transition metal chalcogenides and is expected to inspire further theoretical and experimental studies on this intriguing class of materials.

Source-reported materials — not catalogue approval

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