  Multi-orbital superconductors combine unconventional pairing with complex
band structures, where different orbitals in the bands contribute to a
multitude of superconducting gaps. We here demonstrate a fresh approach using
low-temperature scanning tunneling microscopy (LT-STM) to resolve the
contributions of different orbitals to superconductivity. This approach is
based on STM's capability to resolve the local density of states (LDOS) with a
combined high energy and sub unit-cell resolution. This technique directly
determines the orbitals on defect free crystals without the need for scatters
on the surface and sophisticated quasi-particle interference (QPI)
measurements. Taking bulk FeSe as an example, we directly resolve the
superconducting gaps within the units cell using a 30 mK STM. In combination
with density functional theory calculations, we are able to identify the
orbital character of each gap.
