High electrical conductivity in the epitaxial polar metals LaAuGe and LaPtSb

Abstract

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 (MBE) 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 (STEM) reveals a polar structure with unidirectionally buckled $BC$ (PtSb, AuGe) planes. Magnetotransport measurements demonstrate good metallic behavior with low residual resistivity (${\rho }_{LaAuGe}=59.05$ $\mu \Omega \cdot$cm and ${\rho }_{LaAPtSb}=27.81$ $\mu \Omega \cdot$cm at 2K) and high carrier density ($n_h\sim 10^{21}$ 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, though the degree of direct interlayer $B-C$ bonding is limited by repulsion at the $A-C$ contacts. When combined with insulating hexagonal Heuslers, these materials provide a new platform for fully epitaxial, multiferroic heterostructures.

References in corpus (11)

• A ferroelectric-like structural transition in a metal
• `Ferroelectric' Metals Reexamined: Fundamental Mechanisms and Design Considerations for New Materials
• Hexagonal $ABC$ as semiconducting ferroelectrics
• Hyperferroelectrics: proper ferroelectrics with persistent polarization
• Artificial two-dimensional polar metal at room temperature
• The Dirac-Weyl semimetal: Coexistence of Dirac and Weyl fermions in polar hexagonal $ABC$ crystals
• Intertwined Rashba, Dirac and Weyl Fermions in Hexagonal Hyperferroelectrics
• Coexistence of polar distortion and metallicity in PbTi1-xNbxO3
• Searching for hexagonal analogues of the half-metallic half-Heusler XYZ compounds
• Perspective: Heusler interfaces -- opportunities beyond spintronics?
• Electronically enhanced layer buckling and Au-Au dimerization in epitaxial LaAuSb films

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• Control of polymorphism during epitaxial growth of hyperferroelectric candidate LiZnSb on GaSb (111)B
• Metamagnetism and anomalous magnetotransport properties in rare-earth-based polar semimetals $R$AuGe ($R=$ Dy, Ho, and Gd)
• Semi-adsorption-controlled growth window for half Heusler FeVSb epitaxial films
• Coupled magnetic and structural phase transitions in the antiferromagnetic polar metal Pb2CoOsO6 under pressure
• Single crystal growths and magnetic properties of hexagonal polar semimetals RAuGe (R = Y, Gd-Tm, and Lu)
• Quantum fluctuation of ferroelectric order in polar metals
• Electronic Structure of Kramers Nodal-Line Semimetal YAuGe and Anomalous Hall Effect Induced by Magnetic Rare-Earth Substitution
• Review on ferroelectric/polar metals
• Tunable polar distortions and magnetism in Gd${}_x$La${}_{1-x}$PtSb epitaxial films