Visualization of robust two-dimensional bulk states with suppressed surface state on epitaxial PdCoO2 thin films with bipolar surfaces

Tomoki Kawamoto, Anjana Krishnadas, Chia-Hsiu Hsu, Markel Pardo-Almanza, Yuita Fujisawa, Guoqing Chang, Takayuki Harada, and Yoshinori Okada
Phys. Rev. Materials 7, 024001 – Published 3 February 2023

Abstract

Epitaxial thin films of metallic delafossites are a recent topic of intense investigation due to their intriguing electronic states. Using in situ angle-resolved photoemission spectroscopy, we investigated the electronic states of epitaxial PdCoO2 thin films with high crystalline quality and bipolar surface with mixed termination. On this characteristic surface, we observed a surprisingly prominent bulklike single hexagonal large Fermi surface with suppressed surface state. Firstly, observation of a sharp Fermi surface relies on the minimized atomic scale disorder in our high-quality film surface. Additionally, the predominantly two-dimensional bulk electronic state with the Fermi group velocity parallel to the plane of PdCoO2 is expected to make the near-surface bulklike state less sensitive to the scattering by longer length scale random bipolar surface potentials. Furthermore, the origin of the suppressed surface state can be interpreted by screening of the polarity on the surface, which is qualitatively supported by density functional theory calculation. These findings are invaluable for accelerating the search for exotic functionalities in epitaxial ultrathin films and heterostructures of metallic delafossites.

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  • Received 1 June 2022
  • Revised 26 October 2022
  • Accepted 18 November 2022

DOI:https://doi.org/10.1103/PhysRevMaterials.7.024001

©2023 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Tomoki Kawamoto1,2,*, Anjana Krishnadas1,*, Chia-Hsiu Hsu3, Markel Pardo-Almanza1, Yuita Fujisawa1, Guoqing Chang3, Takayuki Harada4,5,†, and Yoshinori Okada1,‡

  • 1Quantum Materials Science Unit, Okinawa Institute of Science and Technology (OIST), Okinawa 904-0495, Japan
  • 2Department of Applied Physics, the University of Tokyo, Tokyo 113-8656, Japan
  • 3School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798
  • 4MANA, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
  • 5JST, PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan

  • *These authors contributed equally to this work.
  • harada.takayuki@nims.go.jp
  • yoshinori.okada@oist.jp

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Issue

Vol. 7, Iss. 2 — February 2023

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