High electrical conductivity in the epitaxial polar metals LaAuGe and LaPtSb
High electrical conductivity in the epitaxial polar metals LaAuGe and LaPtSb
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DOI：
10.1063/1.5132339
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发表时间：
2019-12-01
期刊：
影响因子：
6.1
通讯作者：
Kawasaki, Jason K.
中科院分区：
文献类型：
--
作者：
Du, Dongxue;Lim, Amber;Kawasaki, Jason K.
极性金属是一类有趣的材料，它们同时具有自由载流子和极性结构畸变。尽管被称为“极性金属”，然而，大多数研究充分的极性金属都是不良的电导体。在这里，我们展示了分子束外延生长的LaPtSb和LaAuGe，两个极性的金属化合物，其电阻率是一个数量级低于充分研究的氧化物极性金属。这些材料属于采用填充纤锌矿结构的ABC金属间化合物的大家族，也称为六方Heusler化合物。扫描透射电子显微镜揭示了一个极性结构与单向屈曲BC（PtSb和AuGe）平面。磁输运测量表明具有低剩余电阻率（在2K下ρ（LaAuGe）= 59.05 μ Ω cm和ρ（LaAPtSb）= 27.81 μ Ω cm）和高载流子密度（n（h）类似于10（21）cm（-3））的良好金属行为。光电子能谱测量确认频带金属性，并与密度泛函理论（DFT）计算的定量协议。通过DFT-化学压和晶体轨道汉密尔顿布居分析，发现尽管层间B-C键的直接成键程度受到A-C接触排斥的限制，但原子填充因子支持结构的极性屈曲。当与预测的铁电六角Heusler相结合时，这些材料为完全外延的多铁性异质结构提供了一个新的平台。
Polar metals are an intriguing class of materials that simultaneously host free carriers and polar structural distortions. Despite the name "polar metal," however, most well-studied polar metals are poor electrical conductors. Here, we demonstrate the molecular beam epitaxial growth of LaPtSb and LaAuGe, two polar metal compounds whose electrical resistivity is an order of magnitude lower than the well studied oxide polar metals. These materials belong to a broad family of ABC intermetallics adopting the stuffed wurtzite structure, also known as hexagonal Heusler compounds. Scanning transmission electron microscopy reveals a polar structure with unidirectionally buckled BC (PtSb and AuGe) planes. Magnetotransport measurements demonstrate good metallic behavior with low residual resistivity (rho(LaAuGe) = 59.05 mu omega cm and rho(LaAPtSb) = 27.81 mu omega cm at 2 K) and high carrier density (n(h) similar to 10(21) cm(-3)). Photoemission spectroscopy measurements confirm the band metallicity and are in quantitative agreement with density functional theory (DFT) calculations. Through DFT-chemical pressure and crystal orbital Hamilton population analyses, the atomic packing factor is found to support the polar buckling of the structure although the degree of direct interlayer B-C bonding is limited by repulsion at the A-C contacts. When combined with predicted ferroelectric hexagonal Heuslers, these materials provide a new platform for fully epitaxial, multiferroic heterostructures.