A correlated insulator at the surface of the polar metal Ca3Ru2O7
Abstract
We investigate the electronic structure at the surface of the correlated oxide Ca3Ru2O7, a low-symmetry ruthenate oxide which hosts an unconventional polar-metal phase. From a combination of angle-resolved photoemission spectroscopy and scanning tunneling spectroscopy measurements, we demonstrate that the surface hosts an insulating phase, a distinct departure from metallicity within the bulk. Utilizing quantitative low-energy electron diffraction in conjunction with electronic structure calculations, we show how this results from a combined surface structure relaxation and the impact of marked electronic correlations in this system. Our findings highlight the proximity of Ca3Ru2O7 to an insulating metallic state, and illustrate how subtle structural distortions can control its emergent electronic phases.
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