Strong Electron Correlation behind the Superconductivity in Ce-Free and Ce-Underdoped High-T_c T′-Cuprates

Novel Electronic State and Superconductivity in the Electron-Doped High-Tc T’-Superconductors

“…Considering both results of ARPES without the AF pseudogap and µSR with the short-range magnetic order, it is likely that Cu spins forming the short-range magnetic order have tiny magnetic moments. That is, the reduction annealing gives rise to not only the change of the long-range AF order to the short-range one but also the reduction of the magnetic moments of Cu spins, which is compatible with the decrease in the internal magnetic field at the muon site estimated from µSR results [22].…”

“…Zero-field (ZF) and longitudinalfield (LF) µSR measurements of Pr 1.3−x La 0.7 Ce x CuO 4+δ with x = 0.10 and La 1.8 Eu 0.2 CuO 4+δ were performed using a pulsed positive muon beam at the Material and Life Science Experimental Facility at J-PARC in Japan and using a continuous positive muon beam at the Paul-Scherrer Institute (PSI) in Switzerland, respectively. Figure 5a,b show the ZF-µSR time spectra of asgrown non-SC and 700 • C-reduced SC samples of La 1.8 Eu 0.2 CuO 4+δ , respectively [22]. For both samples, Gaussian-like slow depolarizations due to nuclear dipole fields are observed at high temperatures, indicating a paramagnetic state of Cu spins.…”

“…The analysis of volume fractions of SC and short-range magnetically ordered regions leads to the detailed information on the electronic state in the T'-cuprates. The magnetic volume fractions were estimated from the µSR results [22]. For the reduced SC La 1.8 Eu 0.2 CuO 4+δ , the volume fraction of the short-range magnetically ordered region is almost 100% in the ground state.…”

“…Yet to date, the mechanism of the undoped superconductivity is unclear. In this review article, we show our recent results relating to the undoped superconductivity in the T'cuprates [21][22][23]. First, we present the characteristics of the electron-doped T'-cuprates including the reduction annealing, conventional phase diagram and undoped superconductivity.…”

Suppression of the antiferromagnetic pseudogap in the electron-doped high-temperature superconductor by protect annealing

“…The short AFM correlation length is consistent with μ SR measurements on PLCCO single crystals with x =0.10 (ref. 33): The rotation of muon spins was observed in as-grown samples, suggesting the existence of long-range AFM order, while in sufficiently protect-annealed samples only fast relaxation was observed, suggesting that AFM correlation is short-ranged. The reduction of the magnitude of the fluctuating spin moment would also contribute to the weakening of the AFM pseudogap.…”