Electronically enhanced layer buckling and Au-Au dimerization in epitaxial LaAuSb films

Abstract

We report the molecular beam epitaxial growth, structure, and electronic measurements of single-crystalline LaAuSb films on Al${}_2$O${}_3$ (0001) substrates. LaAuSb belongs to a broad family of hexagonal $ABC$ intermetallics in which the magnitude and sign of layer buckling have strong effects on properties, e.g., predicted hyperferroelecticity, polar metallicity, and Weyl and Dirac states. Scanning transmission electron microscopy reveals highly buckled planes of Au-Sb atoms, with strong interlayer Au-Au interactions and a doubling of the unit cell. This buckling is four times larger than the buckling observed in other $ABC$s with similar composition, e.g. LaAuGe and LaPtSb. Photoemission spectroscopy measurements and comparison with theory suggest an electronic driving force for the Au-Au dimerization, since LaAuSb, with a 19-electron count, has one more valence electron per formula unit than most stable $ABC$s. Our results suggest that the electron count, in addition to conventional parameters such as epitaxial strain and chemical pressure, provides a powerful means for tuning the layer buckling in ferroic $ABC$s.

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References in corpus (2)

• Searching for hexagonal analogues of the half-metallic half-Heusler XYZ compounds
• Gold-Gold Bonding: The Key to Stabilizing the 19-Electron Ternary Phases LnAuSb (Ln = La-Nd and Sm) as New Dirac Semimetals

Cited by in corpus (1)

• High electrical conductivity in the epitaxial polar metals LaAuGe and LaPtSb