Abstract
In an electronic system with various interactions intertwined, revealing the origin of its many-body ground state is challenging and a direct experimental way to verify the correlated nature of an insulator has been lacking. Here we demonstrate a way to unambiguously distinguish a paradigmatic correlated insulator, a Mott insulator, from a trivial band insulator based on their distinct chemical behavior for a surface adsorbate using , which has been debated between a spin-frustrated Mott insulator or a spin-singlet trivial insulator. We start from the observation of different sizes of spectral gaps on different surface terminations and show that potassium adatoms on these two surface layers behave in totally different ways. This can be straightforwardly understood from distinct properties of Mott and band insulators due to the fundamental difference of the half- and full-filled orbitals involved, respectively. This work not only solves an outstanding problem in this particularly interesting material but also provides a simple touchstone to identify the correlated ground state of electrons experimentally.
- Received 13 November 2020
- Revised 9 March 2021
- Accepted 12 April 2021
DOI:https://doi.org/10.1103/PhysRevLett.126.196405
© 2021 American Physical Society
Physics Subject Headings (PhySH)
synopsis
A Mott Meter
Published 13 May 2021
A new experimental method based on adsorption can indicate whether a material is a Mott insulator or a common insulator.
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