Electronically enhanced layer buckling and Au-Au dimerization in epitaxial LaAuSb films
Electronically enhanced layer buckling and Au-Au dimerization in epitaxial LaAuSb films
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DOI：
10.1103/physrevmaterials.3.024201
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发表时间：
2019-01
影响因子：
3.4
通讯作者：
P. J. Strohbeen;Dongxue Du;Chenyu Zhang;Estiaque H. Shourov;F. Rodolakis;J. McChesney;P. Voyles;J. Kawasaki
中科院分区：
文献类型：
--
作者：
P. J. Strohbeen;Dongxue Du;Chenyu Zhang;Estiaque H. Shourov;F. Rodolakis;J. McChesney;P. Voyles;J. Kawasaki
报道了Al$2$O$3$(0001)衬底上单晶LaAuSb薄膜的分子束外延生长、结构和电子测量。LaAuSb属于六方金属间化合物大家族，其中层屈曲的大小和符号对性质有很大的影响，例如预测的超铁电性、极性金属丰度以及Weyl和Dirac态。扫描电子显微镜显示Au-Sb原子的高度弯曲的平面，具有很强的层间Au-Au相互作用和单位晶胞的加倍。这种屈曲比其他成分相似的$ABC$S的屈曲大四倍，如LaAuGe和LaPtSb。光电子能谱测量和与理论的比较表明，Au-Au的二聚化具有电子驱动力，因为具有19个电子计数的LaAuSb的每个公式单位比最稳定的$ABC$S多一个价电子。我们的结果表明，除了常规的外延应变和化学压力等参数外，电子计数还为调节铁相$ABC$S的层屈曲提供了一个强有力的手段。
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.