Tailoring the low-energy physics of RuO2 by epitaxial strain

ORAL

Abstract

Rutile ruthenium dioxide (RuO2) was long presumed to be a paramagnetic metal with weak electronic correlations, until recent measurements of antiferromagnetism in bulk single crystals by Berlijn et al. Motivated by this discovery to better understand its electronic structure, we synthesized RuO2 thin films by molecular-beam epitaxy on rutile TiO2 substrates and characterized these films using in situ angle-resolved photoemission spectroscopy (ARPES). Comparing our ARPES data with density-functional calculations, we find that: (1.) electron-phonon coupling accounts for most of the modest quasiparticle mass renormalizations observed in RuO2, and (2.) a sizable crystal field splitting in the rutile structure lifts the threefold degeneracy of the t2g manifold spanning the Fermi level (EF), causing strong departures from the prototypical Hund’s metal behavior observed in perovskite-based ruthenates, despite having the same electron count of 4d4. Guided by this understanding of the effective low-energy physics, we explain how epitaxial strain modifies the orbital occupations in RuO2 films grown on different orientations of TiO2 substrates, and discuss how concomitant changes to the density of states near EF feed back into the instability of strained RuO2 towards superconductivity.

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Presenters

  • Jacob Ruf

    Cornell University

Authors

  • Jacob Ruf

    Cornell University

  • Hanjong Paik

    Cornell University

  • Jason Kawasaki

    Univ of Wisconsin, Madison, Cornell University, Wisconsin-Madison, University of Wisconsin, Madison

  • Betul Pamuk

    Cornell University

  • Hari Nair

    Cornell University, Department of Materials Science and Engineering, Kavli Institute at Cornell for Nanoscale Science, Cornell University

  • Nathaniel Schreiber

    Cornell University

  • Ludi Miao

    Cornell University

  • Darrell G. Schlom

    Cornell University, Cornell University, Ithaca, New York 14853, USA, Department of Materials Science and Engineering, Cornell University, Department of Materials Science and Engineering, Kavli Institute at Cornell for Nanoscale Science, Cornell University, Materials Science & Engineering, Cornell University, Department of Materials Science and Engineering,, Cornell University, Materials Science and Engineering, University of Cornell

  • Kyle M Shen

    Cornell University, Department of Physics, Laboratory of Atomic and Solid State Physics, Kavli Institute at Cornell for Nanoscale Science, Cornell University