Electron Confinement, Orbital Ordering, and Orbital Moments in $d^0$-$d^1$ Oxide Heterostructures

Abstract

The (SrTiO${}_3$)${}_m$/(SrVO${}_3$)${}_n$ $d^0-d^1$ multilayer system is studied with first principles methods through the observed insulator-to-metal transition with increasing thickness of the SrVO${}_3$ layer. When correlation effects with reasonable magnitude are included, crystal field splittings from the structural relaxations together with spin-orbit coupling (SOC) determines the behavior of the electronic and magnetic structures. These confined slabs of SrVO${}_3$ prefer $Q_{orb}$=($\pi ,\pi$) orbital ordering of ${\ell }_z=0$ and ${\ell }_z=-1$ ($j_z=-1/2$) orbitals within the plane, accompanied by $Q_{spin}$=(0,0) spin order (ferromagnetic alignment). The result is a SOC-driven ferromagnetic Mott insulator. The orbital moment of 0.75 ${\mu }_B$ strongly compensates the spin moment on the ${\ell }_z=-1$ sublattice. The insulator-metal transition for $n=1\to 5$ (occurring between $n$=4 and $n$=5) is reproduced. Unlike in the isoelectronic $d^0-d^1$ TiO${}_2$/VO${}_2$ (rutile structure) system and in spite of some similarities in orbital ordering, no semi-Dirac point [{\it Phys. Rev. Lett.} {\bf 102}, 166803 (2009)] is encountered, but the insulator-to-metal transition occurs through a different type of unusual phase. For n=5 this system is very near (or at) a unique semimetallic state in which the Fermi energy is topologically determined and the Fermi surface consists of identical electron and hole Fermi circles centered at $k$=0. The dispersion consists of what can be regarded as a continuum of radially-directed Dirac points, forming a "Dirac circle".

9 pages, 8 figures

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• Orbital-assisted metal-insulator transition in VO${}_2$
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• Orbital-quenching-induced magnetism in Ba_2NaOsO_6
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• A single nodal loop of accidental degeneracies in minimal symmetry: triclinic CaAs${}_3$
• Tuning the metal-insulator transition in epitaxial SrVO3 films by uniaxial strain
• Quasiparticle interference on cubic perovskite oxide surfaces
• Electronic structure of V${}_4$O${}_7$: charge ordering, metal-insulator transition and magnetism
• Structural transition in LaVO3/SrVO3 superlattices and its influence on transport properties
• Interface chemical and electronic properties of LaAlO3/SrVO3 heterostructures
• Spin-orbit interaction driven collective electron-hole excitations in a noncentrosymmetric nodal loop Weyl semimetal
• Non-collinear vs collinear description of the Ir-based one-$t_{2g}$ -hole perovskite-related compounds: SrIrO${}_3$ and Sr${}_2$IrO${}_4$
• Accidental Degeneracy in k-space, Geometrical Phase, and the Perturbation of $\pi$ by Spin-orbit Interactions
• Nano-engineering of electron correlation in oxide superlattices
• Nitride Multilayers as a Platform for Parallel Two-Dimensional Electron-Hole Gases: MgO/ScN(111)
• On the ferromagnetic character of (LaVO${}_3$)${}_m$/SrVO${}_3$ superlattices
• The electrothermal conductance and heat capacity of black phosphorus
• Increasing the number of topological nodal lines in semimetals via uniaxial pressure