Topological insulators are a new class of materials, that exhibit robust
gapless surface states protected by time-reversal symmetry. The interplay
between such symmetry-protected topological surface states and symmetry-broken
states (e.g. superconductivity) provides a platform for exploring novel quantum
phenomena and new functionalities, such as 1D chiral or helical gapless
Majorana fermions, and Majorana zero modes which may find application in
fault-tolerant quantum computation. Inducing superconductivity on topological
surface states is a prerequisite for their experimental realization. Here by
growing high quality topological insulator Bi2βSe3β films on a d-wave
superconductor Bi2βSr2βCaCu2βO8+Ξ΄β using molecular beam epitaxy,
we are able to induce high temperature superconductivity on the surface states
of Bi2βSe3β films with a large pairing gap up to 15 meV. Interestingly,
distinct from the d-wave pairing of Bi2βSr2βCaCu2βO8+Ξ΄β, the
proximity-induced gap on the surface states is nearly isotropic and consistent
with predominant s-wave pairing as revealed by angle-resolved photoemission
spectroscopy. Our work could provide a critical step toward the realization of
the long sought-after Majorana zero modes.Comment: Nature Physics, DOI:10.1038/nphys274