Superconductivity in undoped T'-RE2CuO4 with Tc over 30 K

TL;DR

This paper reports the discovery of superconductivity above 30 K in undoped T'-RE2CuO4 thin films, challenging the belief that these materials are Mott insulators, using a simple, cost-effective fabrication process.

Contribution

It demonstrates that undoped T'-RE2CuO4 can be superconducting with high Tc, achieved through low-pressure oxygen firing and reduction, a novel approach in the field.

Findings

Superconductivity observed in undoped T'-RE2CuO4 with Tc over 30 K.

Gd2CuO4 becomes superconducting with Tconset as high as 20 K.

The process is inexpensive and uses metal-organic decomposition.

Abstract

In this article, we report the superconductivity in T'-RE2CuO4 (RE = Pr, Nd, Sm, Eu, and Gd), which have been for a long time believed as a Mott insulator. Our discovery was achieved by using metal-organic decomposition (MOD), an inexpensive and easy-to-implement thin-film process. The keys to prepare the superconducting films are firing with low partial-pressure of oxygen and reduction at low temperatures. The highest Tc of undoped T'-RE2CuO4 is over 30 K, substantially higher than "electron-doped" analogs. Remarkably, Gd2CuO4, even the derivatives of which have not shown superconductivity so far, gets superconducting with Tconset as high as 20 K. The implication of our discovery is briefly discussed.