Density wave ground state and fractional fermions in LaAlO3/SrTiO3 heterostructure

TL;DR

This paper demonstrates that the non-uniform charge distribution in LaAlO3/SrTiO3 heterostructures forms a density wave ground state modeled by an anharmonic lattice, revealing fractional fermions akin to polyacetylene.

Contribution

It establishes a connection between interface reconstruction in heterostructures and density wave states described by a {\lambda}{\phi}4 model, introducing fractional fermions in this context.

Findings

Identification of a density wave ground state in heterostructures.

Application of the {\lambda}{\phi}4 continuum model to interface phenomena.

Prediction of fractional fermions similar to polyacetylene.

Abstract

We show that the non-homogeneous charged layer distribution of the LaAlO 3 /SrT iO 3 heterostructure undergoing interface reconstruction is the density wave ground state of the well known anharmonic lattice model described by the {\lambda}{\phi} 4 continuum model. The two dimensional planar structure of the charged surfaces with alternating polarity leads to an effective one dimensional model, with fermions coupled to the planar distortions acting as long wavelength optical phonons in one dimension. The Hamiltonian with the desired anharmonicity for describing the non-homogeneous density wave type distortion is the same one that describes the fermion number fractionalization in polyacetylene. The general solution of this theory is the Jacobi elliptic sine function sn(x;k), which in the limiting case of lattice distortion being localized gives the kink/anti-kink solution.