The net charge at interfaces between insulators

Abstract

The issue of the net charge at insulating oxide interfaces is shortly reviewed with the ambition of dispelling myths of such charges being affected by covalency and related charge density effects. For electrostatic analysis purposes, the net charge at such interfaces is defined by the counting of discrete electrons and core ion charges, and by the definition of the reference polarisation of the separate, unperturbed bulk materials. The arguments are illustrated for the case of a thin film of LaAlO${}_3$ over SrTiO${}_3$ in the absence of free carriers, for which the net charge is exactly 0.5$e$ per interface formula unit, if the polarisation response in both materials is referred to zero bulk values. Further consequences of the argument are extracted for structural and chemical alterations of such interfaces, in which internal rearrangements are distinguished from extrinsic alterations (changes of stoichiometry, redox processes), only the latter affecting the interfacial net charge. The arguments are reviewed alongside the proposal of Stengel and Vanderbilt [Phys. Rev. B {\bf 80}, 241103 (2009)] of using formal polarisation values instead of net interfacial charges, based on the interface theorem of Vanderbilt and King-Smith [Phys. Rev. B {\bf 48}, 4442 (1993)]. Implications for non-centrosymmetric materials are discussed, as well as for interfaces for which the charge mismatch is an integer number of polarisation quanta.

References in corpus (5)

• Maximally-localized generalized Wannier functions for composite energy bands
• Berry-phase theory of polar discontinuities at oxide-oxide interfaces
• Oxide superlattices with alternating p and n interfaces
• Predicting polarization and nonlinear dielectric response of arbitrary perovskite superlattice sequences
• Theoretical investigation of polarization-compensated II-IV/I-V perovskite superlattices

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• Electrostatic stability of insulating surfaces: Theory and applications
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• Thickness Dependent Carrier Density at the Surface of SrTiO3 (111) Slabs
• Proposal of a one-dimensional electron gas in the steps at the LaAlO${}_3$-SrTiO${}_3$ interface
• Electronic charge redistribution in LaAlO${}_3$(001) thin films deposited at SrTiO${}_3$(001) substrate: First principles analysis and the role of stoichiometry
• Quasiperiodicity and 2D Topology in 1D Charge Ordered Materials
• Giant magnetoelectric effect in pure manganite-manganite heterostructures