Electrodynamic properties of an artificial heterostructured superconducting cuprate

TL;DR

This study investigates the electrodynamic properties of CaCuO$_2$/SrTiO$_3$ heterostructures, revealing strong correlations and similarities with cuprate superconductors, supported by experimental measurements and theoretical calculations.

Contribution

It provides the first detailed infrared conductivity analysis of CCO/STO heterostructures, highlighting the role of correlations and their analogy to natural cuprate superlattices.

Findings

High degree of electronic correlation increases with reduced doping.

Experimental results align with Dynamical Mean-Field Theory calculations.

Cuprate superconductors can be viewed as natural superlattices with disentangled layers.

Abstract

We perform infrared conductivity measurements on a series of CaCuO$_2$/SrTiO$_3$ heterostructures made by the insulating cuprate CaCuO$_2$ (CCO) and the insulating perovkite SrTiO$_3$ (STO). We estimate the carrier density of various heterostructures, with different level of hole doping from the integral of the optical conductivity and we measure the corresponding degree of correlation by estimating the ratio between the Drude weight and the integral of the infrared spectrum. The analysis demonstrates a large degree of correlation, which increases as the doping is reduced. The experimental results can be reproduced by Dynamical Mean-Field Theory calculations which strongly support the role of correlations in the CCO/STO heterostructures and their similarities with the most common cuprate superconductors. Our results suggest that cuprate superconductors can be looked at as natural superlattices, where the properties of the CuO$_2$ conducting planes and charge reservoir blocks can be completely disentangled.