Ising superconductivity and Majorana fermions in transition-metal dichalcogenides

In monolayer transition-metal dichalcogenides (TMDs), electrons in opposite K valleys are subject to opposite effective Zeeman fields, which are referred to as Ising spin-orbit coupling (SOC) fields. The Ising SOC, originating from in-plane mirror symmetry breaking, pins the electron spins to the out-of-plane directions, and results in Ising superconducting states with strongly enhanced upper critical fields. Here, we show that the Ising SOC generates equal-spin-triplet Cooper pairs with spin polarized in the in-plane directions. Importantly, the spin-triplet Cooper pairs can induce superconducting pairings in a half-metal wire placed on top of the TMD and result in a topological superconductor with Majorana end states. Direct ways to detect equal-spin triplet Cooper pairs and the differences between Ising superconductors and Rashba superconductors are discussed.