Long-range charge density wave proximity effect at cuprate-manganate interfaces

TL;DR

This study demonstrates that interfaces with ferromagnetic manganates can significantly enhance and extend the charge density wave state in high-temperature cuprate superconductors, revealing a long-range electronic proximity effect.

Contribution

It provides the first evidence of a long-range charge density wave proximity effect at cuprate-manganate interfaces, enabling manipulation of collective phenomena in metal oxides.

Findings

CDW formation is greatly enhanced at interfaces with La2/3Ca1/3MnO3

The effect persists over several tens of nanometers

Charge carrier concentration is confirmed as the key factor

Abstract

The interplay between charge density waves (CDWs) and high-temperature superconductivity is currently under intense investigation. Experimental research on this issue is difficult because CDW formation in bulk copper-oxides is strongly influenced by random disorder, and a long-range-ordered CDW state in high magnetic fields is difficult to access with spectroscopic and diffraction probes. Here we use resonant x-ray scattering in zero magnetic field to show that interfaces with the metallic ferromagnet La$_{2/3}$Ca$_{1/3}$MnO$_3$ greatly enhance CDW formation in the optimally doped high-temperature superconductor YBa$_2$Cu$_3$O$_{6+\delta}$ ($\bf \delta \sim 1$), and that this effect persists over several tens of nm. The wavevector of the incommensurate CDW serves as an internal calibration standard of the charge carrier concentration, which allows us to rule out any significant influence of oxygen non-stoichiometry, and to attribute the observed phenomenon to a genuine electronic proximity effect. Long-range proximity effects induced by heterointerfaces thus offer a powerful method to stabilize the charge density wave state in the cuprates, and more generally, to manipulate the interplay between different collective phenomena in metal oxides.