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Abstract

Charge-density wave (CDW) and superconductivity, as well as their interplay, are fascinating topics in condensed-matter physics. In this work, we propose a single-layer (SL) CDW material, 1T−TaSi₂N₄, among synthesized two-dimensional (2D) MoSi₂N₄ family. Through first-principles simulations, its stability, vibrational properties, electronic structures, CDW, and superconductivity have been systematically scrutinized. The Ta-d_z² orbitals occupy mainly at the Fermi level and SL 1T−TaSi₂N₄ exhibits intrinsic metallic property. Besides, the CDW transition temperature (T_CDW) is estimated to be ∼500 K by using the temperature dependent effective potential technique. We found that it is the electron-phonon couping (EPC) that drives the CDW to form. Furthermore, its CDW orders can be manipulated by carrier doping and applying strain. At doping of 0.14 h/cell, the CDW instability is effectively suppressed and it changes to a 2D superconductor below ∼21.84 K. Moreover, its superconducting transition temperature T_c under the strain of 10% is ∼10.47 K. Physically, the superconductivity in stabilized 1T−TaSi₂N₄ monolayer is mainly contributed by the EPC between electrons from the Ta-d_z² orbitals and phonon vibrations from the Ta−xy and N−z modes with evident soft phonon mode.