Engineering superconductivity on the surface of Weyl semimetals

Ten years after the experimental discovery of Weyl semimetals, theoretical and experimental work has pointed to the possibility of realizing surface-only superconductivity at relatively high temperatures in these materials. A consensus is developing that this unusual form of superconductivity is supported by surface electronic states unique to Weyl semimetals, known as Fermi arcs. In this work, we show that the topological protection of these exotic states can be exploited to engineer high critical temperatures. Motivated by reports of van Hove singularities on the surface of PtBi$_2$-the first Weyl semimetal in which surface superconductivity was unequivocally linked to its Fermi arcs-we demonstrate how such singularities can be engineered through the deposition of a suitable additional layer. We find that the critical temperature becomes extremely sensitive to the exact value of the chemical potential, and values as large as 20 times the bulk $T_c$ can be achieved. More generally, our results demonstrate how topological protection can be exploited to manipulate surface electronic states, thereby opening experimentally accessible routes toward engineering high-temperature two-dimensional superconductivity and other exotic phases.