Abstract
Iridate oxides display exotic physical properties that arise from the interplay between a large spin–orbit coupling and electron correlations. Here, we present a comprehensive study of the effects of hydrostatic pressure on the electronic transport properties of SrIrO3 (SIO), a system that has recently attracted a lot of attention as potential correlated Dirac semimetal. Our investigations on untwinned thin films of SIO reveal that the electrical resistivity of this material is intrinsically anisotropic and controlled by the orthorhombic distortion of the perovskite unit cell. These effects provide another evidence for the strong coupling between the electronic and lattice degrees of freedom in this class of compounds. Upon increasing pressure, a systematic increase of the transport anisotropies is observed. The anomalous pressure-induced changes of the resistivity cannot be accounted for by the pressure dependence of the density of the electron charge carriers, as inferred from Hall effect measurements. Moreover, pressure-induced rotations of the IrO6 octahedra likely occur within the distorted perovskite unit cell and affect electron mobility of this system.
Highlights
The 5d iridium-based transition metal oxides have attracted huge interest since the spin-orbit coupling (SOC) in these compounds is on similar energy scale to that of electron-correlation or electronic bandwidth [1,2] which may in turn favor new or exotic quantum states [3,4,5,6,7]
In-plane rotations of IrO6 octahedra are suppressed in very thin SIO films grown on SrTiO3 (STO) due to the structural constraints imposed upon octahedral inplane rotations by the cubic substrate and induces a metal-to-insulator transition in films thinner than 4 nm [22]
It was found that the combination of orthorhombic distortion and SOC which introduces unusual thermal expansion of the unit cell [23], which in turn results in an anisotropic electronic transport in SIO films at ambient pressure with smallest resistivity along the c-axis [24]
Summary
The 5d iridium-based transition metal oxides have attracted huge interest since the spin-orbit coupling (SOC) in these compounds is on similar energy scale to that of electron-correlation or electronic bandwidth [1,2] which may in turn favor new or exotic quantum states [3,4,5,6,7]. The electronic transport of strained SIO films depends sensitively on the substrates lattice-mismatch and may display metallic or even insulating character [10]. It was found that the combination of orthorhombic distortion and SOC which introduces unusual thermal expansion of the unit cell [23], which in turn results in an anisotropic electronic transport in SIO films at ambient pressure with smallest resistivity along the c-axis [24]. The application of hydrostatic pressure constitutes an alternative to the more commonly used substitution-induced chemical pressure or fully strained epitaxial growth and allows continuous tuning of the systemsproperties It thereby enables a more systematic investigation of the interplay between electronic and structural degrees of freedom [26,27,28,29].
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