Related papers: Pressure effects in the triangular layered cobalti…
Unconventional superconductivity in bulk materials under ambient pressure is extremely rare among the 3d transition metal compounds outside the layered cuprates and iron-based family. It is predominantly linked to highly anisotropic…
The layered sodium cobalt oxyhydrate superconductor Na0.3CoO2*1.4H2O is shown through X-ray diffraction and thermogravimetric studies to be one of a series of hydrated phases of Na0.3CoO2. Further, it is shown that the material is…
We extend the solid-state nudged elastic band method to handle a non-conserved order parameter - in particular, magnetization, that couples to volume and leads to many observed effects in magnetic systems. We apply this formalism to the…
We have investigated the systematic transport properties of the layered 112-type cobaltite LaBaCo2O5.5 by means of electrical resistivity, magnetoresistance, electroresistance and thermoelectric measurements in various conditions. In order…
The recent observation of a insulator to metal transition (IMT) [I. Loa et al, PRL 87, 125501 (2001)] in pure LaMnO$_3$ at 32 GPa and room temperature, well above the Neel temperature (145 K) and below the Jahn-Teller transition temperature…
Single-crystalline whiskers of thermoelectric cobalt oxide, NaxCoO2, have been grown by an unconventional method from potassium-containing compositions, and their transport properties, and chemical compositions were determined. The growth…
We systematically study the effect of high pressure on the structure, electronic structure and transport properties of 2H-MoS$_2$, based on first-principles density functional calculations and the Boltzmann transport theory. Our calculation…
The sodium-cobalt oxide NaxCoO2+d is a promising candidate for thermoelectric applications since it may possess simultaneously large thermoelectric power and low resistivity. It is difficult to understand the simultaneous appearance of the…
We have performed specific heat and electric resistivity measurements of Na$_{x}$CoO$_{2}$ ($x=0.70$-0.78). Two anomalies have been observed in the specific heat data for $x=0.78$, corresponding to magnetic transitions at $T_{c}=22$ K and…
We have investigated the Pb-substitution effect on the superconductivity of NaCl-type In1-xPbxTe samples obtained using high-pressure synthesis. Polycrystalline samples with x = 0-0.8 were obtained, and the lattice parameter systematically…
Muon spin relaxation ($\mu$SR) measurements on the new layered cobalt oxide superconductor Na$_{0.35}$CoO$_{2}\cdot$1.3H$_{2}$O and its parent, non-superconducting compounds, have revealed unconventional nature of superconductivity through:…
Effect of Ti doping on the electrical transport and magnetic properties of layered Na0.8Co1-xTixO2 compounds has been investigated. The lattice parameters a and c increase with x. A minor amount of Ti doping results in a metal-insulator…
We performed high-pressure transport studies on the flat-band Kagome compounds, Pd$_3$P$_2$(S$_{1-x}$Se$_x$)$_8$ ($x$ = 0, 0.25), with a diamond anvil cell. For both compounds, the resistivity exhibits an insulating behavior with pressure…
We study the effects of temperature on the band structure of the Bi$_2$Se$_3$ family of topological insulators using first-principles methods. Increasing temperature drives these materials towards the normal state, with similar…
It is shown that the empirical relations between transition temperature, normal state conductivity linearly extrapolated to the value at the transition temperature, zero temperature penetration depths, etc., as observed in a rich variety of…
We synthesized powder samples of Na$_{x}$CoO$_{2}\cdot y$H$_{2}$O changing the volume of the water in the hydration process, then investigated their superconducting properties,. It was proved that the volume of water is one of key…
We have successfully grown single crystalline NaFeAs with cobalt or phosphor doping. Bulk superconductivity occurs in NaFe$_{0.95}$Co$_{0.05}$As at 19 K while much higher transition temperature is observed in NaFeAs$_{0.8}$P$_{0.2}$, in…
Here we present a systematic study of the effects of pressure on the superconducting and spin/charge density wave (SDW/CDW) transitions of Ba$_{1-x}$Na$_x$Ti$_2$Sb$_2$O (x = 0, 0.10, and 0.15) by means of resistivity measurements. For x = 0…
In order to understand the experimentally proposed phase diagrams of NaxCoO2.yH2O, we theoretically study the CoO2-layer-thickness dependence of magnetic and superconducting (SC) properties by analyzing a multiorbital Hubbard model using…
Here we present results of accurate wet-chemical redox analyses, revealing that the oxidation number of cobalt in the newly discovered CoO2-layer superconductor, NaxCoO2 yH2O (x ~ 0.36, y ~ 1.3) is ~ 3.46. This value is significantly lower…