Multivalley Superconductivity in Monolayer Transition Metal Dichalcogenides

Area of Science:

• Condensed Matter Physics
• Materials Science
• Solid State Physics

Background:

• Ising superconductivity in transition metal dichalcogenides (TMDs) exhibits unique antisymmetric spin textures.
• The role of the Q valley, characterized by giant spin splitting, in the superconductivity of 2H-TMDs remains unclear.

Purpose of the Study:

• To investigate the involvement of Q valleys in superconductivity within heavily doped semiconducting 2H-TMDs.
• To explore the relationship between multivalley population and the emergence of superconductivity and nonlinear Hall effects.

Main Methods:

• Fabrication of high-quality monolayer WS2 on hexagonal boron nitride (hBN) flakes.
• Utilized ionic gating to induce and tune superconductivity.
• Measured critical temperature and nonlinear Hall effect.
• Performed first-principles calculations to corroborate experimental findings.

Main Results:

• Achieved ionic-gating induced superconductivity in monolayer WS2 with a record high critical temperature of approximately 6 K.
• Observed an emergent nonlinear Hall effect, indicative of an additional high-mobility electronic channel.
• Corroborated that this channel arises from the population of Q valleys, alongside K valleys.

Conclusions:

• Multivalley population, specifically involving both K and Q valleys, is a prerequisite for developing Ising superconductivity in 2H-TMDs.
• The involvement of Q valleys provides crucial insights into the spin-textured Fermi surface of Ising superconductors.
• This work expands understanding of superconductivity mechanisms in the broader family of transition metal dichalcogenides.