Emergent charge density wave featuring quasi-one-dimensional chains in Ta-intercalated bilayer 2H−TaS2 with coexisting superconductivity

Abstract

Recently, intercalation emerges as an effective way to manipulate ground-state properties and enrich quantum phase diagrams of layered transition metal dichalcogenides (TMDCs). In this work, we focus on fully Ta-intercalated bilayer 2H−TaS2 with a stoichiometry of Ta3S4, which has recently been experimentally synthesized. Based on first-principles calculations, we computationally show the suppression of an intrinsic 3×3 charge-density wave (CDW) in the TaS2 layer, and the emergence of a 2×1 CDW in intercalated Ta layer. The formation of the CDW in Ta3S4 is triggered by strong electron-phonon coupling (EPC) between the d-like orbitals of intercalated Ta atoms via the imaginary phonon modes at M point. A 2×1 CDW structure is identified, featuring quasi-one-dimensional Ta chains, attributable to the competition between the CDW displacements associated with potential CDW vectors (qCDWs). Superconductivity is found to coexist with the 2×1 CDW in Ta3S4, with an estimated superconducting transition temperature (Tc) of 3.0 K, slightly higher than that of bilayer TaS2. The Ta3S4 structures of non-CDW, 2×1 CDW, and 2×2 CDW can be switched by strain. Our work enriches the phase diagram of TaS2, offers a candidate material for studying the interplay between CDW and superconductivity, and highlights intercalation as an effective way to tune the physical properties of layered materials.

Source-reported materials — not catalogue approval

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