Metallic phase in the metal-intercalated higher fullerene Rb8.8(7)C84

A new material of higher fullerene, RbxC84, was synthesized by intercalating Rb metal into C-84 crystals. The RbxC(84) crystals showed a simple cubic (sc) structure with lattice constant, a, of 16.82 (2) angstrom at 6.5 K, and 16.87 (2) angstrom at 295 K. The Rietveld refinements were achieved with the space group, Pa (3) over bar, based on a model that the C-2 axis of D2d-C84 aligned along [111]. The sample composition was determined to be Rb-8.8(7) C-84. The ESR spectrum at 303 K was composed of a broad peak with peak-to-peak linewidth Delta H-pp of 220 G, and a narrow peak with Delta H-pp of 24 G. Temperature dependence of the broad peak clearly showed a metallic behavior. The metallic behavior was discussed based on a theoretical calculation. This finding of new metallic phase in a higher fullerene is the first step for a development of new types of fullerene materials with novel physical properties such as superconductivity.</p

Crystal structure and phase transitions across the metal-superconductor boundary in the SmFeAsO1-xFx (0 < x < 0.20) family

The fluorine-doped rare-earth iron oxyarsenides, REFeAsO1-xFx (RE =rare earth) have recently emerged as a new family of high-temperature superconductors with transition temperatures (Tc) as high as 55 K (refs 1-4). Early work has provided compelling evidence that the undoped parent materials exhibit spin-density-wave (SDW) antiferromagnetic order and undergo a structural phase transition from tetragonal to orthorhombic crystal symmetry upon cooling.5 Both the magnetic and structural instabilities are suppressed upon doping with fluoride ions before the appearance of superconductivity.6,7 Here we use high-resolution synchrotron X-ray diffraction to study the structural properties of SmFeAsO1-xFx (0 < x < 0.20) in which superconductivity emerges near x ~ 0.07 and Tc increases monotonically with doping up to x ~ 0.20.8 We find that orthorhombic symmetry survives through the metal-superconductor boundary well into the superconducting regime 2 and the structural distortion is only suppressed at doping levels, x > 0.15 when the superconducting phase becomes metrically tetragonal. Remarkably this crystal symmetry crossover coincides with reported drastic anomalies in the resistivity and the Hall coefficient8 and a switch of the pressure coefficient of Tc from positive to negative,9 thereby implying that the low-temperature structure plays a key role in defining the electronic properties of these superconductors

Crystal structure of the new FeSe1-x superconductor

The newly discovered superconductor FeSe1-x (x=0.08, Tconset=13.5 K at ambient pressure rising to 27 K at 1.48 GPa) exhibits a structural phase transition from tetragonal to orthorhombic below 70 K at ambient pressure - the crystal structure in the superconducting state shows remarkable similarities to that of the REFeAsO1-xFx (RE = rare earth) superconductorsComment: Chem. Commun. (2008

Mott localization in the correlated superconductor Cs3C60 resulting from the molecular Jahn-Teller effect

Cs3C60 is a correlated superconductor under pressure, but an insulator under ambient conditions. The mechanism causing this insulating behavior is the combination of Mott localization and the dynamic Jahn-Teller effect. We show evidence from infrared spectroscopy for the dynamic Jahn-Teller distortion. The continuous change with temperature of the splitting of infrared lines is typical Jahn-Teller behavior, reflecting the change in population of solid-state conformers. We conclude that the electronic and magnetic solid-state properties of the insulating state are controlled by molecular phenomena. We estimate the time scale of the dynamic Jahn-Teller effect to be above 10^(-11) s and the energy difference between the conformers less than 20 cm-1

Optimized unconventional superconductivity in a molecular Jahn-Teller metal

Understanding the relationship between the superconducting, the neighboring insulating, and the normal metallic state above Tc is a major challenge for all unconventional superconductors. The molecular A3C60 fulleride superconductors have a parent antiferromagnetic insulator in common with the atom-based cuprates, but here, the C603– electronic structure controls the geometry and spin state of the structural building unit via the on-molecule Jahn-Teller effect. We identify the Jahn-Teller metal as a fluctuating microscopically heterogeneous coexistence of both localized Jahn-Teller–active and itinerant electrons that connects the insulating and superconducting states of fullerides. The balance between these molecular and extended lattice features of the electrons at the Fermi level gives a dome-shaped variation of Tc with interfulleride separation, demonstrating molecular electronic structure control of superconductivity

Synthesis of the extended phenacene molecules, [10]phenacene and [11]phenacene, and their performance in a field-effect transistor

The [10]phenacene and [11]phenacene molecules have been synthesized using a simple repetition of Wittig reactions followed by photocyclization. Sufficient amounts of [10]phenacene and [11]phenacene were obtained, and thin-film FETs using these molecules have been fabricated with SiO2 and ionic liquid gate dielectrics. These FETs operated in p-channel. The averaged measurements of field-effect mobility, , were 3.1(7) × 10-2 and 1.11(4) × 10-1 cm2 V-1 s-1, respectively, for [10]phenacene and [11]phenacene thin-film FETs with SiO2 gate dielectrics. Furthermore, [10]phenacene and [11]phenacene thin-film electric-double-layer (EDL) FETs with ionic liquid showed low-voltage p-channel FET properties, with values of 3(1) and 1(1) cm2 V-1 s-1, respectively. This study also discusses the future utility of the extremely extended π-network molecules [10]phenacene and [11]phenacene as the active layer of FET devices, based on the experimental results obtained

The Oligomeric States of the Photosystems and the Light-Harvesting Complexes in the Chl b-Less Mutant

The reversible associations between the light-harvesting complexes (LHCs) and the core complexes of PSI and PSII are essential for the photoacclimation mechanisms in higher plants. Two types of chlorophylls, chlorophyll a and chlorophyll b, both function in light harvesting and are required for the biogenesis of the photosystems. Chlorophyll b-less plants have been studied to determine the function of the LHCs because the chlorophyll b deficiency has severe effects specific to the LHCs. Previous studies have shown that the amounts of the LHCs, especially the LHCII trimer, were decreased in the mutants; however, it is still unclear whether chlorophyll b is required for the assembly of the LHCs and for the association of the LHCs with PSI and PSII. Here, to reveal the function of chlorophyll b in the LHCs, we investigated the oligomeric states of the LHCs, PSI and PSII in the Arabidopsis chlorophyll b-less mutant. A two-dimensional blue native-PAGE/SDS-PAGE demonstrated that the PSI-LHCI supercomplex was fully assembled in the absence of chlorophyll b, whereas the trimeric LHCII and PSII-LHCII supercomplexes were not detected. The PSI-NAD(P)H dehydrogenase (NDH) supercomplexes were also assembled in the mutant. Furthermore, we detected two forms of monomeric LHC proteins. The faster migrating forms, which were detected primarily in the mutant, were likely apo-LHC proteins, whereas the slower migrating forms were likely the LHC proteins that contained chlorophyll a. These findings increase our understanding of the chlorophyll b function in the assembly of LHCs and the association of the LHCs with PSI, PSII and NDH