Novel Cu-based dz2 order at a YBa2Cu3O7/ manganite interface

TL;DR

This study uncovers a new Cu-based density wave order at YBa2Cu3O7/manganite interfaces with unique orbital and wave vector properties, revealing novel interfacial phenomena in cuprate heterostructures.

Contribution

It reports the discovery of a previously unobserved Cu density wave order with dz2 orbital character at cuprate/manganite interfaces, induced by interfacial charge transfer and doping.

Findings

Identified a Cu density wave with Q=0.096 r.l.u.

The order has a large correlation length (~40 nm).

It exhibits a dz2 orbital character instead of the usual dx2-y2.

Abstract

The interplay of nearly degenerate orders in quantum materials can lead to a myriad of emergent phases. A prominent case is that of the high-Tc cuprates for which the relationship between superconductivity and a short-ranged, incommensurate charge density wave in the CuO2 planes involving the dx2-y2 orbitals (Cu-CDW) is a subject of great current interest. Strong modifications of the strength and coherence of this Cu-CDW have been achieved by applying large magnetic fields, uniaxial pressure, or via the interfacial coupling in cuprate/manganite multilayers. However, such modifications do not alter the dominant orbital character. Here we investigate cuprate/manganite multilayers with resonant inelastic X-ray scattering (RIXS) and show that a new kind of Cu-based density wave order can be induced that has not been previously observed in the cuprates. This order has an unusually small wave vector of Q = 0.096 reciprocal lattice units (r.l.u.), a large correlation length of about 40 nm, and a predominant dz2 orbital character, instead of the typical dx2-y2 character. Its appearance is determined by the hole doping of the manganite which is a key parameter controlling the interfacial charge transfer and orbital reconstruction. We anticipate that the observation of a previously unknown type of density wave order at the YBCO interface will allow for fresh perspectives on the enigmatic relation between superconductivity and charge order (CO) in the cuprates.