Xin-Zhi Li, Zhen-Bo Qi, Quansheng Wu, Wen-Yu He

Topological superconductivity has attracted significant attention due to its potential applications in quantum computation, but its experimental realization remains challenging. Recently, monolayer T$_{\textrm{d}}$-MoTe$_2$ was observed to exhibit gate tunable superconductivity, and its in-plane upper critical field exceeds the Pauli limit. Here, we show that an in-plane magnetic field beyond the Pauli limit can drive the superconducting monolayer T$_{\textrm{d}}$-MoTe$_2$ into a topological superconductor. The topological superconductivity arises from the interplay between the in-plane Zeeman coupling and the unique \emph{Ising plus in-plane SOC} in the monolayer T$_{\textrm{d}}$-MoTe$_2$. The \emph{Ising plus in-plane SOC} plays the essential role to enable the effective $p_x+ip_y$ pairing. Importantly, as the essential \emph{Ising plus in-plane SOC} in the monolayer T$_{\textrm{d}}$-MoTe$_2$ is generated by an in-plane polar field, our proposal demonstrates that applying an in-plane magnetic field to a gate tunable 2D superconductor with an in-plane polar axis is a feasible way to realize topological superconductivity.