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Charge Fractionalization in Oxide Heterostructures: A Field Theoretical Model

LaAlO$_{3}$/SrTiO$_{3}$ heterostructure with polar and non-polar constituents has been shown to exhibit interface metallic conductivity due to fractional charge transfer to the interface. The interface reconstruction by electron redistribution along (001) orientation, in which half of an electron is transferred per two dimensional unit cell to the adjacent planes, resulting in a net transfer of half of the charge, to both the interface and top most atomic planes, has been ascribed to a polar discontinuity at the interface in the Polar Catastrophe model. This avoids the divergence of electrostatic potential, as the number of layers are increased, producing an oscillatory electric field and finite potential. Akin to the description of charge fractionalization in quasi one-dimensional polyacetylene by the field theoretic Jackiw-Rebbi model with fermions interacting with topologically non-trivial background field, we show an analogous connection between polar catastrophe model and Bell-Rajaraman model, where the charge fractionalization occurs in the soliton free sector as an end effect.