Soft-Mode-Phonon-Mediated Unconventional Superconductivity in Monolayer 1T^{'}-WTe_{2}.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Monolayer 1T'-WTe$_{2}$ has been experimentally tuned to superconductivity via electrostatic gating.
• Understanding the mechanisms behind superconductivity in 2D materials is crucial for next-generation electronics.

Purpose of the Study:

• To theoretically investigate the phonon-mediated superconductivity in monolayer 1T'-WTe$_{2}$ under charge doping.
• To elucidate the role of phonon modes and Fermi surface nesting in the emergence of superconductivity.
• To explore the pairing symmetry and anisotropy of the upper critical field.

Main Methods:

• Theoretical study of phonon-mediated superconductivity using charge doping.
• Analysis of soft-mode phonons and their momentum dependence.
• Investigation of Fermi surface nesting conditions.
• Consideration of experimentally observed anisotropy in the upper critical field (H$_{c2}$).

Main Results:

• Superconductivity emerges in the electron-doping regime due to soft-mode phonons with specific momentum.
• No superconductivity or relevant soft-mode phonons are observed in the hole-doping regime.
• A superconducting dome is identified, linked to electron doping-induced changes in Fermi surface nesting.
• The superconducting state likely features unconventional equal-spin-triplet pairing in the A$_{u}$ channel (C$_{2h}$ point group).

Conclusions:

• Soft-mode phonons are essential for electron-doping-induced superconductivity in monolayer 1T'-WTe$_{2}$.
• The findings explain the doping-dependent superconductivity and the strong anisotropy of H$_{c2}$.
• This work provides a framework for understanding superconductivity in other gated transition metal dichalcogenides.