Revealing the single electron pocket of FeSe from within a single orthorhombic domain

We measure the electronic structure of FeSe from within individual orthorhombic domains. Enabled by
an angle-resolved photoemission spectroscopy beamline with a highly focused beamspot (nano-ARPES), we
identify clear stripe-like orthorhombic domains in FeSe with a length scale of approximately 1-5 m. Our
photoemission measurements of the Fermi surface and band structure within individual domains reveal a single
electron pocket at the Brillouin zone corner. This result provides clear evidence for a one-electron pocket
electronic structure of FeSe, observed without the application of uniaxial strain, and calls for further theoretical
insight into this unusual Fermi surface topology. Our results also showcase the potential of nano-ARPES for the
study of correlated materials with local domain structures.