Related papers: Applying experimental constraints to a one-dimensi…
Pressure effects on a recently discovered BiS2-based superconductor Bi2(O,F)S2 (Tc = 5.1 K) were examined via two different methods; high pressure resistivity measurement and high pressure annealing. The effects of these two methods on the…
Two single crystalline samples with the same nominal composition of Rb0.8Fe2Se2 prepared via slightly different precursor routes under the same thermal processing conditions were investigated at ambient and high pressures. One sample was…
Charge density wave (CDW) instability is often found in phase diagrams of superconductors such as cuprates and certain transition-metal dichalcogenides. This proximity to superconductivity triggers the question on whether CDW instability is…
Recently, several types of BiS2-based superconductor such as Bi4O4S3, REO1-xFxBiS2 (RE: rare earth) and Sr1-xLaxFBiS2 have been discovered. In this study, we have investigated the crystal structure and the superconducting properties for two…
Crystal structure and physical properties of the novel BiS2-based layered superconductors are briefly reviewed. Superconductivity in the BiS2-based layered compounds is induced by electron doping into the BiS2 conduction layers. The…
Quasi-two-dimensional layered BiSe, a natural super-lattice with Bi2Se3-Bi2-Bi2Se3 units, has recently been predicted to be a dual topological insulator, simultaneously weak topological insulator as well as topological crystalline…
The mechanism of unconventional superconductivity in iron-based superconductors (IBSs) is one of the most intriguing questions in current materials research. Among non-oxide IBSs, (Ba$_{1-x}$K$_x$)Fe$_2$As$_2$ has been intensively studied…
In 2012, we discovered superconductivity in Bi4O4S3 and LaO1-xFxBiS2, whose crystal structures are composed of alternate stacks of a BiS2-type conduction layer and a blocking layer. Since the discovery, many related superconductors and…
We performed combined infrared reflection and ellipsometry measurements of the in-plane optical reponse of single crystals of the pnictide high temperature superconductor BaFe$_{1.87}$Co$_{0.13}$As$_{2}$ with $T_{c}$ = 24.5 K. We observed…
The relationship between the pseudogap and superconductivity remains a central puzzle in the physics of cuprates. Hydrostatic pressure provides a clean tuning parameter free from chemical disorder, yet probing the microscopic energy scales…
We describe high-Tc superconductivity in layered materials within a BCS theory as a BEC of massless-like Cooper pairons satisfying a linear dispersion relation, and propagating within quasi-2D layers of finite width defined by the charge…
Since the discovery of superconductivity in the cuprates two decades ago, it has been firmly established that the CuO_2 plane is consequential for high T_C superconductivity and a host of other very unusual properties. A new family of…
The superfluid density and superconducting gaps of superconducting RbFe_{2}As_{2} have been determined as a function of temperature, magnetic field and hydrostatic pressure by susceptibility and muon-spin spectroscopy measurements. From the…
The superconducting energy gap of $\rm Ba_{1-x}K_xBiO_3$ has been measured by tunneling. Despite the fact that the sample was macroscopically single phase with very sharp superconducting transition $T_c$ at 32~$K$, some of the measured…
Resistive and magnetization properties have been measured in BiS$_2$-based samples CeO$_{1-x}$F$_{x}$BiS$_{2}$ with a systematic substitution of O with F (0 $<$ x $<$ 0.6). In contrast to the band structure calculations, it is found that…
We report appearance of superconductivity in CeO0.5F0.5BiS2. The bulk polycrystalline samples CeOBiS2 and CeO0.5F0.5BiS2 are synthesized by conventional solid state reaction route via vacuum encapsulation technique. Detailed structural…
The London penetration depth, $\lambda$, is directly related to the density, $n_{s}$, of the Cooper pairs ($\lambda^{2}\propto 1/n_{s}$) and its variation with temperature provides valuable insight into the pairing mechanism. Here we study…
We investigate the superconducting-gap anisotropy in one of the recently discovered BiS$_2$-based superconductors, NdO$_{0.71}$F$_{0.29}$BiS$_2$ ($T_c$ $\sim$ 5 K), using laser-based angle-resolved photoemission spectroscopy. Whereas the…
We present our investigations on the superconducting properties of monolayers of FeSe$_{0.5}$Te$_{0.5}$ grown on the 3D topological insulator Bi$_{2}$Se$_{1.2}$Te$_{1.8}$ using low temperature scanning tunneling spectroscopy (STS). While…
Although phase diagrams can be leveraged to investigate high transition temperature (high-$T_c$) superconductivity, the issue has not been discussed thoroughly. In this study, we elucidate the phase diagram of the overdoped side of…