Electron Doping of Cuprates via Interfaces with Manganites

TL;DR

This paper explores the theoretical possibility of electron doping in undoped high-temperature cuprates through interfaces with manganites, potentially inducing superconductivity with minimal disorder.

Contribution

It provides a detailed theoretical analysis and modeling framework predicting charge transfer and doping at oxide interfaces, opening new avenues for superconductivity research.

Findings

Fermi level of manganites is above the upper Hubbard band of cuprates

Charge transfer at interfaces can induce electron doping in cuprates

Antiferromagnetic manganites are more conducive to inducing superconductivity

Abstract

The electron doping of undoped high-$T_c$ cuprates via the transfer of charge from manganites (or other oxides) using heterostructure geometries is here theoretically discussed. This possibility is mainly addressed via a detailed analysis of photoemission and diffusion voltage experiments, which locate the Fermi level of manganites above the bottom of the upper Hubbard band of some cuprate parent compounds. A diagram with the relative location of Fermi levels and gaps for several oxides is presented. The procedure discussed here is generic, allowing for the qualitative prediction of the charge flow direction at several oxide interfaces. The addition of electrons to antiferromagnetic Cu oxides may lead to a superconducting state at the interface with minimal quenched disorder. Model calculations using static and dynamical mean-field theory, supplemented by a Poisson equation formalism to address charge redistribution at the interface, support this view. The magnetic state of the manganites could be antiferromagnetic or ferromagnetic. The former is better to induce superconductivity than the latter, since the spin-polarized charge transfer will be detrimental to singlet superconductivity. It is concluded that in spite of the robust Hubbard gaps, the electron doping of undoped cuprates at interfaces appears possible, and its realization may open an exciting area of research in oxide heterostructures.