Abstract
In the hole-doped cuprates, a small number of carriers suppresses antiferromagnetism and induces superconductivity. In the electron-doped cuprates, on the other hand, superconductivity appears only in a narrow window of high-doped Ce concentration after reduction annealing, and strong antiferromagnetic correlation persists in the superconducting phase. Recently, Pr1.3−xLa0.7CexCuO4 (PLCCO) bulk single crystals annealed by a protect annealing method showed a high critical temperature of around 27 K for small Ce content down to 0.05. Here, by angle-resolved photoemission spectroscopy measurements of PLCCO crystals, we observed a sharp quasi-particle peak on the entire Fermi surface without signature of an antiferromagnetic pseudogap unlike all the previous work, indicating a dramatic reduction of antiferromagnetic correlation length and/or of magnetic moments. The superconducting state was found to extend over a wide electron concentration range. The present results fundamentally challenge the long-standing picture on the electronic structure in the electron-doped regime.
Highlights
In the hole-doped cuprates, a small number of carriers suppresses antiferromagnetism and induces superconductivity
By measuring the Fermi surface (FS) area, we found that this superconducting state with suppressed antiferromagnetism was extended over a wide electron concentration range
The change induced by the protect annealing is clear in the band image plots (Fig. 2d–f), and corresponding energy distribution curves (EDCs; Fig. 2g–i) along the cuts through the node, the hot spot and the anti-node for each sample
Summary
In the hole-doped cuprates, a small number of carriers suppresses antiferromagnetism and induces superconductivity. In thin films[21,22] and powdered samples[23,24] of e-HTSCs, superconductivity was found even without Ce doping Inspired by those studies, Adachi et al.[25] further improved the reduction annealing method of Brinkmann et al by using powders instead of polycrystals, and successfully synthesized bulk superconducting single crystals of Pr1.3 À xLa0.7CexCuO4 (PLCCO) with x 1⁄4 0.10. They call this new reduction annealing method protect annealing method.
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