Hole depletion and localization due to disorder in insulating PrBa2Cu3O7-d: a Compton scattering study

TL;DR

This study investigates the cause of insulating behavior in PrBa2Cu3O7-d by measuring electron momentum density, revealing that disorder from Pr substitution suppresses wavefunction coherence and leads to localization, with potential for superconductivity through improved growth methods.

Contribution

It demonstrates that Pr substitution disorder causes localization in PrBa2Cu3O7-d, and suggests growth techniques can restore superconductivity.

Findings

PrBa2Cu3O7-d shows suppressed wavefunction coherence length.

Disorder from Pr substitution causes metal-insulator transition.

Improved growth methods can produce superconducting PrBa2Cu3O7-d.

Abstract

The (mostly) insulating behaviour of PrBa2Cu3O7-d is still unexplained and even more interesting since the occasional appearance of superconductivity in this material. Since YBa2Cu3O7-d is nominally iso-structural and always superconducting, we have measured the electron momentum density in these materials. We find that they differ in a striking way, the wavefunction coherence length in PrBa2Cu3O7-d being strongly suppressed. We conclude that Pr on Ba-site substitution disorder is responsible for the metal-insulator transition. Preliminary efforts at growth with a method to prevent disorder yield 90K superconducting PrBa2Cu3O7-d crystallites.