We report on the first successful output of electrons directly from photosystem I (PSI) of thermophilic cyanobacteria to the gate of a field-effect transistor (FET) by bypassing electron flow via a newly designed molecular wire, i.e., artificial vitamin K(1), and a gold nanoparticle; in short, this newly manufactured photosensor employs a bio-functional unit as the core of the device. Photo-electrons generated by the irradiation of molecular complexes composed of reconstituted PSI on the gate were found to control the FET. This PSI-bio-photosensor can be used to interpret gradation in images. This PSI-FET system is moreover sufficiently stable for use exceeding a period of 1 year.

We prepared Ag(x)(As0.4Se0.6)(100-x) chalcogenide glasses by a melt-quenching method and measured their linear and nonlinear optical properties to evaluate their potential applications to all-optical ultrafast switching devices. Their nonlinear refraction and absorption were measured by the Z-scan method at 1.05 microm. The addition of Ag to As2Se3 glass led to an increase in the nonlinear refractive index without introducing an increase in the nonlinear absorption coefficient. The glass with a Ag content of x = 20 at. % revealed high nonlinearity ranging from 2000 to 27,000 times that of fused silica, depending on the incident optical intensity.

We report unusual effects of nonmagnetic impurities on the spin-triplet superconductor Sr2RuO4. The substitution of nonmagnetic Ti 4+ for Ru 4+ induces localized-moment magnetism characterized by unexpected Ising anisotropy with the easy axis along the interlayer c direction. Furthermore, for x(Ti) ≥ 0.03 magnetic ordering occurs in the metallic state with the remnant magnetization along the c axis. We argue that the localized moments are induced in the Ru 4+ and/or oxygen ions surrounding Ti 4+ and that the ordering is due to their interaction mediated by itinerant Ru-4d elecrtons with strong spin fluctuations.

In Sr2RuO4 the spin excitation spectrum is dominated by incommensurate fluctuations at q=(0.3 0.3 qz), which arise from Fermi-surface nesting. We show that upon Ti substitution , known to suppress superconductivity, a short range magnetic order develops with a propagation vector (0.307 0.307 1). This finding confirms that superconducting Sr2RuO4 is extremely close to an incommensurate spin density wave instability. In addition, the ordered moment in Sr2Ru0.91Ti0.09O4 points along the c-direction, which indicates that the incommensurate spin fluctuations exhibit the anisotropy required to explain a p-wave spin triplet pairing.Sr 2 RuO 4 the only superconducting layered perovskite isostructural with the cuprates has attracted considerable interest [1]. Though there is some evidence that the pairing in this compound is unconventional and of triplet character, the coupling mechanism is still subject of debate [2,3,4,5]. Inspired by the ferromagnetism in the 3D-perovskite SrRuO 3 , it has been proposed that the coupling is mediated by ferromagnetic fluctuations [6], for which, however, no experimental evidence has been found so far. Instead, band structure calculations reveal magnetic fluctuations at incommensurate positions arising from Fermi-surface nesting in the 1D-like bands associated to the d xz -and d yz -orbitals [7]. Inelastic neutron scattering has perfectly confirmed this nesting scenario [8] with peaks in the dynamic magnetic susceptibility appearing at q=(0.3 0.3 q z ). We use the notation Q=τ +q, with Q the scattering vector, q the propagation vector in the first Brillouin-zone and τ a reciprocal lattice vector; all vectors are given in reciprocal lattice units corresponding to (The pairing in Sr 2 RuO 4 could be rather complicated since the Fermi surface is formed by three bands. Of the three bands only two contribute directly to the dynamical nesting. The third band, the γ-band associated to the d xy -orbitals, is thought to be closer to ferromagnetism with a possibly stronger role for the superconducting pairing. However, recent calculations still do not give evidence for ferromagnetic fluctuations arising from the γ-band [9]. In addition there is no evidence for a dominant role of ferromagnetic fluctuations in the transport properties [3], and the superconducting transition temperature decreases upon pressure increase [10] , again in a region far away from the superconducting compound; nevertheless this observation indicates some ferromagnetic instability also in the 214-system. Replacing a part of the Ru by non-magnetic fourvalent Ti (configuration 3d 0 ) leads to magnetic anomalies even for very low Ti-concentration, x>0.025 in Sr 2 Ru 1−x Ti x O 4 [13]. These anomalies have been interpreted in terms of an appearance of weak magnetic moments around Ti impurities. In this work we show that these Ti-doped samples exhibit incommensurate magnetic ordering corresponding to the Fermi-surface nesting instability. Concerning the pure compound, one may conclude that it is much closer to an incommensurate ...

Nach Anregung mit Licht überträgt das P700 des Photosystems I (PS I) Elektronen auf eine Goldoberfläche (siehe Bild). Dabei kommt ein neuartiges molekulares Verbindersystem zum Einsatz, in dem ein künstlicher molekularer Draht, der auf der Goldoberfläche angeordnet ist, durch Rekonstitution mit PS I verbunden wurde. Die Analyse der Kinetik des Photoelektronentransfers belegt die Abgabe von Elektronen aus PS I sowie die Effektivität des molekularen Drahts.