Zoology of spin and orbital fluctuations in ultrathin oxide films

Abstract

Many metallic transition-metal oxides turn insulating when grown as films that are only a few unit-cells thick. The microscopic origins of these thickness induced metal-to-insulator transitions however remain under dispute. Here, we simulate the extreme case of a monolayer of an inconspicuous correlated metal -- the strontium vanadate SrVO${}_3$ -- deposited on a SrTiO${}_3$ substrate. Crucially, our system can have a termination to vacuum consisting of either a SrO or a VO${}_2$ top layer. While we find that both lead to Mott insulating behavior at nominal stoichiometry, the phase diagram emerging upon doping -- chemically or through an applied gate voltage -- is qualitatively different. Indeed, our many-body calculations reveal a cornucopia of nonlocal fluctuations associated with (in)commensurate antiferromagnetic, ferromagnetic, as well as stripe and checkerboard orbital ordering instabilities. Identifying that the two geometries yield crystal-field splittings of opposite signs, we elucidate the ensuing phases through the lens of the orbital degrees of freedom. Quite generally, our work highlights that interface and surface reconstruction and the deformation or severing of coordination polyhedra in ultra-thin films drive rich properties that are radically different from the material's bulk physics.

10 pages, 8 figures

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Cited by in corpus (5)

• Toward Functionalized Ultrathin Oxide Films: the Impact of Surface Apical Oxygen
• Dual Bethe-Salpeter equation for the multi-orbital lattice susceptibility within dynamical mean-field theory
• Charge self-consistent density functional theory plus ghost rotationally-invariant slave-boson theory for correlated materials
• Second-order phase transitions and divergent linear response in dynamical mean-field theory
• Confinement-Induced Isosymmetric Metal-Insulator Transition in Ultrathin Epitaxial V2O3 Films