arXiv subjects

Tomohisa Takamatsu

Publications and source records attributed to Tomohisa Takamatsu.

3 recordsLinked to original sources

arXiv2021

Reduction annealing effects on the crystal structure of $T^{\prime}$-type La$_{1.8}$Eu$_{0.2}$CuO$_{4+α-δ}$

We performed neutron powder diffraction measurements on the as-sintered (AS) and oxygen-reduced (OR) La$_{1.8}$Eu$_{0.2}$CuO$_{4+α-δ}$ (LECO). The structural parameters for oxygens in AS and OR samples refined by the Rietveld analysis are almost identical to those of the reference system, Pr$_{2}$CuO$_{4+α-δ}$. Thus, the two systems are comparable in terms of the structural changes in oxygens due to the annealing, although superconductivity appears only in LECO.

cond-mat.supr-con↗

arXiv2020

Electron-Doping Effect on Tc in the Undoped (Ce-Free) Superconductor T'-La1.8Eu0.2CuO4 Studied by the Fluorine Substitution for Oxygen

We have succeeded in synthesizing electron-doped polycrystalline bulk samples of T'-La1.8Eu0.2CuO4-yFy (y = 0 - 0.15) by the fluorination of undoped (Ce-free) T'-La1.8Eu0.2CuO4 using NH4F. The magnetic susceptibility measurements have revealed that the superconducting transition temperature, Tc, increases with increasing y, exhibits the maximum of 23 K at y = 0.025, and decreases. The dome-like dependence of Tc on the doped carrier concentration in the T'-type (La,Eu)-based cuprates is explained in terms of the pairing mediated by spin fluctuations based on the d-p model calculation [K. Yamazaki et al., J. Phys.: Conf. Ser. 871, 012009 (2017)].

cond-mat.supr-con↗

arXiv2016

Pairing Symmetry Studied from Impurity Effects in the Undoped Superconductor T'-La$_{1.8}$Eu$_{0.2}$CuO$_4$

We have investigated the effects of magnetic Ni and nonmagnetic Zn impurities on the superconductivity in undoped T'-La$_{1.8}$Eu$_{0.2}$CuO$_4$ (T'-LECO) with the Nd$_2$CuO$_4$-type structure, using the polycrystalline bulk samples, to clarify the pairing symmetry. It has been found that both suppression rates of the superconducting transition temperature $T_\mathrm{c}$ by Ni and Zn impurities are nearly the same and are very similar to those in the optimally doped and overdoped regimes of hole-doped T-La$_{2-x}$Sr$_{x}$CuO$_4$ with the K$_2$NiF$_4$-type structure. These results strongly suggest that the superconductivity in undoped T'-LECO is of the $d$-wave symmetry and is mediated by the spin fluctuation.

cond-mat.supr-con↗