Scanning tunneling spectroscopy with superconducting tips of Al

We present scanning tunneling spectroscopy measurements at 0.1 K using tips made of Al. At zero field, the atomic lattice and charge density wave of 2H–NbSe2 are observed, and under magnetic fields the peculiar electronic properties of vortices are precisely resolved. The tip density of states is influenced by the local magnetic field of the vortex, providing a new probe for the magnetic field at nanometric sizes.