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We report dye-degradation effects of a semiconductor LiBiO3 revealed under illumination of a conventionally used white fluorescent light. Optical absorbance spectra of LiBiO3 were broadened so smoothly, with the absorption edge penetrated to around 730 nm, that the material was able to absorb a wide range of visible light. Results showed that solution of a standard dye, methylene blue, was degraded completely after 4 h illumination. Furthermore, the value of total organic carbon decreased 70% in the decolorized solution, suggesting that the molecular form of the original methylene blue was mineralized effectively to nonorganic fragments by the photoinduced oxidization effect. Moreover, the wavelength dependence of apparent photonic efficiency was evaluated using a standard Xe lamp coupled with monochromatic filters. These results were interpreted from the viewpoint of this material’s electronic structure.

We observe several non-Fermi liquid behaviors in the normal-state transport properties of CeMIn 5 (M: Rh and Co) under pressure at low temperatures: (1) The dc-resistivity shows T -linear dependence, ρ xx ∝ T . (2) The magnitude of Hall coefficient | R H | increases rapidly with decreasing temperature, and reaches a value much larger than | 1 / ne | at low temperatures. (3) The magnetoresistance displays T - and H -dependence that strongly violate Kohler's rule, and is well scaled by the tangent of the Hall angle, Δ ρ xx / ρ xx ∝ tan 2 Θ H . These non-Fermi liquid properties in the electron transport are remarkably pronounced when the AF fluctuations are enhanced in the vicinity of the quantum critical point. Since all of these salient features have been also reported for high- T c cuprates, we infer that the non-Fermi liquid transport properties capture universal features of strongly correlated electron systems in the presence of strong antiferromagnetic fluctuations.

Effects of pressure on the physical properties are very important for understanding highly correlated electron systems, in which pressure-induced attractive phenomena such as superconductivity and magnetically ordered non-Fermi liquid have been observed. Up to now, many scientists have developed a lot of high pressure apparatus for each purpose. In this paper, we present the very small “palm cubic-anvil high-pressure apparatus” for precise electric transport measurements under high pressure up to 8 GPa. The most outstanding characteristic of this pressure cell is its compactness. This cell enables us to measure absolute values of electrical resistivity, magneto-resistance and Hall coefficient at various temperatures. The details of our palm cubic high-pressure apparatus are introduced, and some neutron experimental results at room temperature are discussed.

We showed how the charge order in (DI-DCNQI) 2 Ag is melted by pressure, by investigations of the NMR spectra and the resistivity parallel and perpendicular to the conducting c -axis. When the system is pressurized, the second-order-transition temperature of the charge ordering is lowered and the disproportionation ratio is depressed. Under higher pressures, the transition changes into first-order one and eventually it vanishes at 21.6 kbar. At a low-pressure and high-temperature region, temperature dependence of ρ // and ρ ⊥ are contrasting. The melting mechanism of the charge ordering is very likely due to the “dimensional crossover”. Furthermore, in the high-pressure metallic region, curious T 3 dependence of the resistivity is observed, implying unprecedented electron-electron scattering mechanism.

Pressure-induced superconductivity in a spin-ladder cuprate Sr2Ca12Cu24O41 was investigated on a microscopic level by using 63Cu nuclear magnetic resonance (NMR) under a pressure of 3.5 GPa. We found a fully gapped superconducting state, and the superconductivity is stable at magnetic fields close to the conventional Pauli limit. The superconducting gap was observed in addition to a spin gap which occurs in a separated temperature range.

The LDA band-structure calculations have been performed for the insulating triclinic phase of the thio-spinel compound, CuIr 2 S 4 , which appears below the metal–insulator transition temperature, ...

We present evidence for the quasi one-dimensional (1D) antiferromagnetism of CuO in the framework of the Heisenberg model. Our result supports the speculations and conclusions made by earlier authors. We also present experimental evidence which explains the reason for CuO to be a quasi 1D antiferromagnet in spite of appearing to have a 3D structure.

We report the pressure effects on lattice constants, magnetic susceptibility, specific heat and electrical resistivity in the orthorhombic PrCu 2 . Anisotropic compression is realized to be κ a ≈κ c

We have investigated the low-temperature phase appearing below To = 17.5 K in URu2Si2 by means of 29Si nuclear magnetic resonance (NMR) in a pressure range from 0 to 17.5 kbar across the pressure-induced phase transition at Pc = 15 kbar. At pressures below Pc, we have observed the 29Si NMR lines arising from antiferromagnetic (AF) and paramagnetic (PM) regions in the sample, giving evidence for a phase-separated AF ordering below To. The AF region increases in volume fraction with increasing pressure up to Pc. In the PM region, the temperature-dependence of the nuclear spin–lattice relaxation rate at Si sites shows a rapid decrease below To, strongly suggesting the occurrence of a phase transition driven by a hidden order parameter. As applied pressure exceeds Pc, the AF ordering appears uniformly at To throughout the sample. In the pressure range from 0 to 17.5 kbar, the magnitude of the internal field at Si sites in the AF region remains constant (~ 920 Oe), which indicates that the AF ordered moment is unchanged by pressure across Pc.

Resistivity ( ρ ) measurements on Magneli phases V 7 O 13 and V 8 O 15 were performed under high pressures up to 3.5GPa. We have achieved a pressure-induced transition from an antiferromagnetic metal to a paramagnetic metal (PM) at critical pressures P c ≈3.4 and 3.3 GPa for V 7 O 13 and V 8 O 15 , respectively. The critical behavior of ρ ( T ) near P c turned out to be quite unusual in that no noticeable precursor effect was observed. This strongly contrasts with the canonical quantum critical point behavior observed in chemically modified systems such as Ni(S,Se) 2 and V 2 O 3 . We propose that the presence of two distinct Fermi surface segments is responsible for the observed unusual behaviors.

The superconductive Cu1−xZnxIr2S4 (x=0.3,0.4 and 0.5) system was studied by measuring the high-pressure resistivity. It was found that the applied pressure induced a superconductor-to-semiconductor transition. The pressure also results in a characteristic temperature T ∗ , where the derivative of resistivity to the temperature shows a local minimum, in the normal states for x=0.4 and 0.5 samples. We discuss the result in terms of phase separations and bipolaron formation.

The Ni–Cr–Al Russian alloy was prepared. Its magnetic and mechanical properties were better than those of MP35N alloy. We fabricated the a piston–cylinder-type hybrid high-pressure cell using the Ni–Cr–Al alloy. It has been found that the maximum working pressure can be repeatedly raised to 3.5 GPa at T = 2 K without any difficulties.

The variations of the superconducting transition temperature Tc and the metal–insulator (MI) transition temperature TMI were investigated as a function of pressure in the superconducting Cu1 −xZnxIr2S4 (0.3 ≤ x ≤ 0.5) system. The experiment was performed by measuring the temperature dependence of resistance under the pressures up to 1.5 GPa. It is shown that the external pressure destroys the superconductivity, and gives rise to the MI transitions. The result is discussed in terms of the stabilization of the insulating phase at high pressures and the phase separation associated with the charge segregation. It is proposed that the BCS Cooper pairs compete with the proposed bipolarons under certain pressures.

X-ray diffraction of a single crystal of PrRu4P12 has been studied at ambient pressure. PrRu4P12 has a filled skutterudite-type structure; space group: Im3, lattice constant: a=8.055(4) A, Z=2, Dcalc=5.826 g/cm3. Positional parameters and interatomic distances in the phosphide were determined. By use of synchrotron radiation, powder X-ray diffraction patterns of PrRu4P12 were measured up to 50 GPa at room temperature. The lattice constant monotonically decreases with increasing pressure. The cell volume vs. pressure curve for PrRu4P12 is fitted with the Birch equation of state. The bulk modulus of the phosphide is 207±12 GPa. The resistivity of PrRu4P12 was measured as a function of temperature at high pressures. The metal to insulator transition is found at around 62 K under ambient pressure. The transition temperature (TMI) rapidly increases with pressure at the rate of about 0.9 K/GPa up to 4.5 GPa. Above 6 GPa, TMI abruptly decreases with increasing pressure. The semiconductor-like behavior below TMI for PrRu4P12 is markedly suppressed at around 8 GPa. The metal to insulator transitions at low temperatures and high pressures are discussed.

Temperature dependent resistivities of Magneli phases Ti n O 2 n -1 ( n =4,5,6), which contains two Ti 3+ and ( n -2) Ti 4+ per unit formula, are measured under various pressures up to 3.5 GPa, to investigate the nature of the two step transitions from a metal to bipolaronic insulators. We found that the pressure dependence of the transition temperatures is critically changes with the density of Ti 3+ . In Ti 4 O 7 , the low temperature bipolaronic phase can be suppressed very rapidly with pressure and the high temperature metallic state is stabilized down to almost T =0 limit at 3.5 GPa. Ti 5 O 9 shows much reduced pressure dependence. In Ti 6 O 11 , eventually, the transition temperatures hardly depend on the applied pressure. We propose that this critical change of the pressure effect originates from a subtle interplay between electron-lattice interaction and electron correlations (inter-site Coulomb repulsions).

In this article, various materials used for the fabrication of high-pressure apparatus are reviewed. Stresses working on each part of the apparatus are considered and a guideline for the selection of suitable materials is given on the basis of their mechanical and physical properties. Especially, the relation of the material strength to the generated pressure is explained in the case of the piston-cylinder type high-pressure clamp cell. It is also emphasized that the processing is important for the materials strength and the performance of high-pressure apparatus. In connection with recent topics of the Ni-based Russian alloy (NiCrAl alloy) and MP35N, some of their materials properties are introduced.

We have developed a clamped piston-cylinder high-pressure cell using NiCrAl alloy and have performed de Haas–van Alphen effect measurements on UGe 2 under hydrostatic pressures up to 17.6 kbar, which exceeds the critical pressure P c where the Curie temperature T C vanishes. We have found that a discontinuous change of the Fermi surface occurs across P c . Quasiparticle effective masses are substantially enhanced near 13 kbar, where the T x anomaly, which occurs below T C in the ferromagnetic phase, is suppressed. Heavy masses (∼40 m e ) are observed near P c on both the ferromagnetic and paramagnetic sides.

The measurements of the electrical resistivity ρ and the thermopower S of single crystal EuCo2P2 have been performed at temperatures from 1.5 to 300 K under hydrostatic pressures up to 3 GPa and in magnetic fields up to 10 T. The temperature dependences of ρ and S show drastic changes at a critical pressure Pc, which indicates a large modification of the electronic structure around the Fermi level due to the valence transition from Eu to Eu. In the low-pressure phase with magnetic Eu and nonmagnetic Co, the magnetic field dependences of ρ and S show sudden decrease at B ≈ 7 T, implying a metamagnetic transition. On the other hand, no drastic change in ρ(B) and S(B) curves is observed in the high-pressure phase with nonmagnetic Eu and magnetic Co.

We report measurements of ac magnetic susceptibility ${\ensuremath{\chi}}_{\text{ac}}$ and de Haas--van Alphen (dHvA) oscillations in ${\mathrm{KFe}}_{2}$${\mathrm{As}}_{2}$ under high pressure up to 24.7 kbar. The pressure dependence of the superconducting transition temperature ${T}_{c}$ changes from negative to positive across ${P}_{c}\ensuremath{\sim}18$ kbar, as previously reported. The ratio of the upper critical field to ${T}_{c}$, i.e., ${B}_{c2}/{T}_{c}$, is enhanced above ${P}_{c}$, and the shape of the ${\ensuremath{\chi}}_{\text{ac}}$ versus field curves qualitatively changes across ${P}_{c}$. dHvA oscillations smoothly evolve across ${P}_{c}$, indicating no drastic change in the Fermi surface up to 24.7 kbar. Three dimensionality increases with pressure, while effective masses show decreasing trends. We suggest a crossover from a nodal to a full-gap $s$ wave as a possible explanation.

The structural phase transition in a thiospinel CuIr 2 S 4 compound which is associated with a metal-to-insulator transformation at approximately 230 K was studied by in-situ low-temperature transmission electron microscopy. It was directly revealed that the structural transition is characterized by the formation of fine {110} twin lamellae and the appearance of additional electron diffraction spots along the * , * and * directions of the room-temperature cubic CuIr 2 S 4 . On the basis of results of electron diffraction analysis, the lattice structure and symmetry of the CuIr 2 S 4 low-temperature insulating phase were determined. Furthermore, we found that the characteristic additional diffraction spots for the insulating phase became quite faint or disappeared when the temperature decreased below approximately 50 K. This suggests a subsequent structural change in the insulating CuIr 2 S 4 at extremely low temperatures.

Magnetic susceptibility and electrical resistivity in the metal–insulator (MI) transition of a mixed-valent Ti-oxide system, Y 1− x Ca x TiO 3 , are investigated at high pressure. This system exhibits obviously the first-order temperature-induced MI transition at x =0.35–0.4. In the low temperature metallic phase, susceptibility, χ ( T ), is strongly suppressed with pressure. On the other hand, in the high temperature semiconductiong phase χ ( T ) obeying the Curie–Weiss law is affected weakly by applying pressure. Below the MI transition temperature resistivity, ρ ( T ), shows the characteristic Fermi liquid behavior, ρ = ρ 0 + AT 2 . The coefficient of the T 2 -term in resistivity, A , and the residual resistivity, ρ 0 , decrease rapidly with pressure, while following the simple relation of A(x, P)∝ρ 0 (x, P) . A scaled temperature-composition phase diagram shows that the first-order transition terminates at both the lower and upper critical points and A , ρ 0 and χ are enhanced enormously at the lower critical point. We present scalings between susceptibility and resistivity in the metallic state taken into account the distribution of the Kondo temperature.

We present results for the charged-particle multiplicity distribution at midrapidity in Au-Au collisions at square root of [s(NN)] = 130 GeV measured with the PHENIX detector at RHIC. For the 5% most central collisions we find dN(ch)/d eta(vertical line eta = 0) = 622+/-1(stat)+/-41(syst). The results, analyzed as a function of centrality, show a steady rise of the particle density per participating nucleon with centrality.