Yoichi Tanabe

Multifunctional Porous Graphene for High‐Efficiency Steam Generation by Heat Localization

Multifunctional nanoporous graphene is realized as a heat generator to convert solar illumination into high-energy steam. The novel 3D nanoporous graphene demonstrates a highly energy-effective steam generation with an energy conversation of 80%.

Bicontinuous Nanoporous N‐doped Graphene for the Oxygen Reduction Reaction

Bicontinuous nanoporous N-doped graphene with tunable pore size is synthesized by nanoporous Ni-based chemical vapor deposition. The novel 3D graphene material shows an outstanding catalytic activity towards the oxygen reduction reaction with a low onset potential of -0.08 V and a high kinetic current density of 8.2 mA cm(-2) at -0.4 V.

High-quality three-dimensional nanoporous graphene.

We report three-dimensional (3D) nanoporous graphene with preserved 2D electronic properties, tunable pore sizes, and high electron mobility for electronic applications. The complex 3D network comprised of interconnected graphene retains a 2D coherent electron system of massless Dirac fermions. The transport properties of the nanoporous graphene show a semiconducting behavior and strong pore-size dependence, together with unique angular independence. The free-standing, large-scale nanoporous graphene with 2D electronic properties and high electron mobility holds great promise for practical applications in 3D electronic devices.

Both electron and hole Dirac cone states in Ba(FeAs)2 confirmed by magnetoresistance.

Quantum transport of Dirac cone states in the iron pnictide Ba(FeAs)(2) with a d-multiband system is studied by using single crystal samples. Transverse magnetoresistance develops linearly against the magnetic field at low temperatures. The transport phenomena are interpreted in terms of the zeroth Landau level by applying the theory predicted by Abrikosov. The results of the semiclassical analyses of a two carrier system in a low magnetic field limit show that both the electron and hole reside as the high mobility states. Our results show that pairs of electron and hole Dirac cone states must be taken into account for an accurate interpretation in iron pnictides, which is in contrast with previous studies.

Superconducting Volume Fraction in Overdoped Regime of La2-xSrxCuO4: Implication for Phase Separation from Magnetic-Susceptibility Measurement

We have grown a single crystal of La 2- x Sr x CuO 4 in which the Sr concentration, x , continuously changes from 0.24 to 0.29 in the overdoped regime and obtained many pieces of single crystals with different x values by slicing the single crystal. From detailed measurements of the magnetic susceptibility, χ, of each piece, it has been found that the absolute value of χ at the measured lowest temperature 2 K, |χ 2 K |, on field cooling rapidly decreases with increasing x as well as the superconducting (SC) transition temperature. As the value of |χ 2 K | is regarded as corresponding to the SC volume fraction in a sample, it has been concluded that a phase separation into SC and normal-state regions occurs in a sample of La 2- x Sr x CuO 4 in the overdoped regime.We have grown a single crystal of La 2- x Sr x CuO 4 in which the Sr concentration, x , continuously changes from 0.24 to 0.29 in the overdoped regime and obtained many pieces of single crystals with different x values by slicing the single crystal. From detailed measurements of the magnetic susceptibility, χ, of each piece, it has been found that the absolute value of χ at the measured lowest temperature 2 K, |χ 2 K |, on field cooling rapidly decreases with increasing x as well as the superconducting (SC) transition temperature. As the value of |χ 2 K | is regarded as corresponding to the SC volume fraction in a sample, it has been concluded that a phase separation into SC and normal-state regions occurs in a sample of La 2- x Sr x CuO 4 in the overdoped regime.

Electric transport of a single-crystal iron chalcogenide FeSe superconductor: Evidence of symmetry-breakdown nematicity and additional ultrafast Dirac cone-like carriers

An SDW antiferromagnetic (SDW-AF) low temperature phase transition is generally observe and the AF spin fluctuations are considered to play an important role for the superconductivity paring mechanism in FeAs superconductors. However, a similar magnetic phase transition is not observed in FeSe superconductors, which has caused considerable discussion. We report on the intrinsic electronic states of FeSe as elucidated by transport measurements under magnetic fields using a high quality single crystal. A mobility spectrum analysis, an ab initio method that does not make assumptions on the transport parameters in a multicarrier system, provides very import and clear evidence that another hidden order, most likely the symmetry broken from the tetragonal C4 symmetry to the C2 symmetry nematicity associated with the selective d-orbital splitting, exists in the case of superconducting FeSe other than the AF magnetic order spin fluctuations. The intrinsic low temperature phase in FeSe is in the almost compensated semimetallic states but is additionally accompanied by Dirac cone like ultrafast electrons

Cu spin dynamics in the overdoped regime of La2-xSrxCu1-yZnyO4 probed by muon spin relaxation

\sim

Similarity between Ni and Zn impurity effects on the superconductivity and Cu-spin correlation in La2-xSrxCu1-yNi yO4 high-Tc cuprates: A comparison based on the hole trapping by Ni

10

Magnetic-Field-Induced Enhancement of the Vortex Pinning in the Overdoped Regime of La2-xSrxCuO4: Relation to the Microscopic Phase Separation

^4

In-plane topological p-n junction in the three-dimensional topological insulator Bi 2− x Sb x Te 3− y Se y

cm