Termination-dependent electronic structure of LaFeAsO revealed by nano-ARPES

LaFeAsO is the parent compound of the so-called ``1111” family of iron-based superconductors – the family in which superconductivity was first discovered and in which the highest reported superconducting transition temperatures have been found. Despite its initial preeminence, its experimental electronic structure still remains an unsolved mystery. We report the experimental electronic structures as measured on both LaO and FeAs terminations using photoemission spectroscopy with a sub-micron focused beam-spot (nano-ARPES). Our data reveal very different band dispersions and core-level spectra for the different surface terminations. Our measurements are consistent with the theoretical calculations taking into account the polar charge and surface relaxations in the system [1], and give reliable assignments to the various band dispersions previously observed with a macroscopic beam spot. Our results show how nano-ARPES can now be used to study materials, and even strongly correlated electron systems, which present multiple surface terminations.

[1] Helmut Eschrig et al., Phys. Rev. B 81, 155447(2010)
[2] Sungwon Jung et al., Timur K. Kim (to appear)