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We report the sulfur isotope effect on transition temperature in a BiS2-based superconductor Bi4O4S3. Polycrystalline samples of Bi4O4S3 were prepared using 32S and 34S isotope chemicals. From magnetization analyses, the isotope exponent…
In conventional superconductors, the electron pairing that allows superconductivity is caused by exchange of virtual phonons, which are quanta of lattice vibration. For high-transition-temperature (high-Tc) superconductors, it is far from…
We report the electrical resistivity measurements under pressure for the recently discovered BiS2-based layered superconductors Bi4O4S3 and La(O,F)BiS2. In Bi4O4S3, the transition temperature Tc decreases monotonically without a distinct…
A large number of compounds which contain BiS$_{2}$ layers exhibit enhanced superconductivity upon electron doping. Much interest and research effort has been focused on BiS$_{2}$-based compounds which provide new opportunities for…
BiCh2-based superconductors (Ch: S, Se) are a new series of layered superconductor. However, mechanisms for the emergence of superconductivity in BiCh2-based superconductors have not been clarified. In this study, we have investigated…
The newly discovered BiS$_2$-based LaO$_{1-x}$F$_{x}$BiS$_2$ ($x$=0.5) becomes superconductive at $T_c$=2.5 K. Electrical resistivity and magnetization measurements are performed under pressure to determine the pressure dependence of the…
The effects of pressure on the superconducting properties of a Bi-based layered superconductor La2O2Bi3Ag0.6Sn0.4S6, which possesses a four-layer-type conducting layer, have been studied through the electrical resistance and magnetic…
Superconductivity in novel bismuth-sulphur superconductors has attracted large research efforts, both experimental and theoretical, but a consensus on the nature of superconductivity in these materials has yet to be reached. Using density…
Very recently a new family of layered materials, containing BiS2 planes was discovered to be superconducting at temperatures up to Tc=10 K, raising questions about the mechanism of superconductivity in these systems. Here, we present…
Layered \textit{Ln}OBiS$_2$ compounds with \textit{Ln} = La, Ce, Pr, Nd, and Yb can be rendered conducting and superconducting via two routes, substitution of F for O or the tetravalent ions Ti, Zr, Hf, and Th for trivalent \textit{Ln}…
Electrical resistivity measurements on La$_{1-x}$Sm$_{x}$O$_{0.5}$F$_{0.5}$BiS$_{2}$ ($x$ = 0.1, 0.3, 0.6, 0.8) have been performed under applied pressures up to 2.6 GPa from 2 K to room temperature. The superconducting transition…
We examined the effect of Pb substitution in the layered superconductor LaO0.5F0.5Bi1-xPbxS2 (x=0~0.15) through the measurements of the resistivity, thermal expansion, specific heat, and Seebeck coefficient. These transport and thermal…
We have investigated the Se isotope effect in layered bismuth chalcogenide (BiCh2-based) superconductor LaO0.6F0.4Bi(S,Se)2 with 76Se and 80Se. For all examined samples, the Se concentration, which is linked to the superconducting…
The isotope effect in the superconducting transition temperature is anomalous if the isotope coefficient $\alpha<0$ or $\alpha>1/2$. In this work, we show that such anomalous behaviors can naturally arise within the…
Exotic superconductivity has often been discovered in materials with a layered (two-dimensional) crystal structure. The low dimensionality can affect the electronic structure and can realize high transition temperatures (Tc) and/or…
Through the solid state reaction method, we synthesized a new BiSe2-based superconductor Sr0:5La0:5FBiSe2 with superconducting transition temperature Tc?3.8 K. A strong diamagnetic signal below Tc in susceptibility ?(T) is observed…
Recently, new layered superconductors having a BiS2-type conduction layer have been discovered. NdO1-xFxBiS2 is a typical BiS2-based superconductor with a maximum Tc of 5.4 K. In this study, the effect of element substitution within the…
Measurements of electrical resistivity were performed between 3 and 300 K at various pressures up to 2.8 GPa on the BiS2-based superconductors LnO0.5F0.5BiS2 (Ln = Pr, Nd). At lower pressures, PrO0.5F0.5BiS2 and NdO0.5F0.5BiS2 exhibit…
The pressure effect on the newly discovered charge-transferred BiS$_2$-based superconductor, Eu$_3$Bi$_2$S$_4$F$_4$, with a $T_c$ of 1.5 K at ambient pressure, is investigated by transport and magnetic measurements. Accompanied with the…
We investigate the external hydrostatic pressure effect on the superconducting transition temperature (Tc) of new layered superconductors Bi4O4S3 and NdO0.5F0.5BiS2. Though the Tc is found to have moderate decrease from 4.8 K to 4.3 K…