  An external magnetic field is needed to drive a nanowire in proximity to an
s-wave superconductor into a topological regime which supports Majorana end
states. However, a magnetic field generally suppresses the proximity
superconducting gap induced on the nanowire. In recent experiments using InSb
nanowires coupled to Al, the induced proximity gap vanishes at magnetic fields
B~1T. This results in a small superconducting gap on the wire and a narrow
topological regime which is proportional to the strength of the magnetic field.
In this work, we show that by placing nanowires in proximity to recently
discovered Ising superconductors such as the atomically thin transition-metal
dichalcogenide(TMD) NbSe2, the topological superconducting gap on the wire can
maintain at a large magnetic field as strong as B~10T. This robust topological
superconducting gap is induced by the unique equal-spin triplet Cooper pairs of
the parent Ising superconductor. The strong magnetic field allows a topological
regime ten times larger than those in InSb wires coupled to Al. Our work
establishes a realistic platform for building robust Majorana-based qubits.
