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

## TL;DR

This study demonstrates the growth and analysis of LaAuSb films, revealing significant Au-Au dimerization driven by electron count, which influences their structural and electronic properties, including potential ferroelectric and topological states.

## Contribution

It introduces the epitaxial growth of LaAuSb films and uncovers electron-driven layer buckling and Au-Au dimerization as key factors affecting their properties.

## Key findings

- Highly buckled Au-Sb planes observed via electron microscopy
- Au-Au interactions lead to unit cell doubling
- Electronic measurements suggest electron count drives dimerization

## 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.