Emergence of intrinsic superconductivity in monolayer W2N3

Abstract

Two-dimensional (2D) materials possessing intrinsic superconductivity with high transition temperature and unconventional pairing are highly desired, but their realizations are few and far between. Recently, W2N3 nanosheets down to three layers were successfully prepared [Yu et al., Adv. Mater. 30, 1805655 (2018)]. By performing solid ab initio calculations based on the anisotropic Migdal-Eliashberg theory, we predict that monolayer W2N3 is an unexplored intrinsic (without the assistance of external gating, strain, or a special substrate) 2D superconductor with large electron-phonon coupling (EPC) and high critical temperature Tc=38K accompanied with a single and broad superconducting gap ∼7.5 meV. The ratio between the gap and the critical temperature is much larger than the value derived from Bardeen-Cooper-Schrieffer (BCS) theory, further confirming the strong coupling feature of monolayer W2N3. The extremely strong EPC originates from the large deformation potential of low-frequency acoustic phonons rather than Fermi-surface nesting. Due to the partially filled d orbitals, electron-electron correlation leads to remarkable enhancement of EPC based on frozen phonon analysis. Here, Tc can be further enhanced via hydrogen passivation based on the McMillian-Allen-Dynes formula. In addition, the symmetry-restricted spin-orbit coupling (SOC) brings forth exotic type-I Ising pairing whose in-plane upper critical field is far beyond the Pauli paramagnetic limit. Our predictions provide a fascinating and highly feasible platform for realizing high-temperature 2D superconductivity and studying the interplay between electron-phonon coupling, electron-electron correlation, and SOCs.

Source-reported materials — not catalogue approval

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