Photoresponse of La1.85_{1.85}Sr0.15_{0.15}CuO4_{4} nanostrip

We report the fabrication and photoresponse of 5 nm thick La$_{1.85}$Sr$_{0.15}$CuO$_{4}$ nanostrip with a width of 100nm. The I-V characteristics of the nanostrip show a hysteresis and a sharp voltage jump at $I_{c}$. The $J_{c}$(3K) of the nanostrip is 2.3 x 10$^{7}$ A/cm$^{2}$. The nanostrip exhibits photoresponse signals when illuminated by a pulse laser at 1560 nm wavelength with a bias current just below $I_{c}$. The height of the signal reduces as the optical intensity decreases and disappears below -10 dBm. The signal also decreases as the temperature increases, but it exists up to 30 K. These results suggest the possibility of La$_{1.85}$Sr$_{0.15}$CuO$_{4}$ nanostrip as single-photon detector (SSPD, SNSPD) working at high temperature by further reducing the cross-section of the strip

In-situ epitaxial growth of superconducting La-based bilayer cuprate thin films

We investigate the epitaxial growth of bilayer cuprate La2CaCu2O6+\delta using pure ozone as an oxidant, and find that even the crystal with parent composition without cation substitution can show metallic behavior with the aid of epitaxial strain effect. The hole concentration is controlled simply by excess-oxygen doping, and the films grown under the optimum conditions exhibit superconductivity below 30 K. This is the first result on the superconductivity of bilayer La2CaCu2O6+\delta induced purely by the excess oxygen.Comment: 5 pages, 3 figures, To appear in Phys. Rev. B, Rapid Communication

In-situ angle-resolved photoemission study of MBE-grown (La, Ce)2CuO4 thin films

We have performed in-situ angle-resolved photoemission spectroscopy on the electron doped cuprate superconductor La2-xCexCuO4 (x = 0.1) using high-quality films grown by molecular beam epitaxy. The obtained photoemission spectra were free from dirt peaks. In addition, the time evolution of the spectra due to impurity adsorption is rather gradual, and the sample surface is stable even at ambient temperature, which is in contrast with previous reports on bulk Nd2-xCexCuO4 (NCCO) single crystals. The energy distribution curves show clear dispersions near the Fermi energy (EF) with some EF crossings. The resultant Fermi surface is hole-like and centered around (pi, pi), which essentially agrees with that predicted for NCCO by band calculations and also with the experimentally determined Fermi surface of optimally doped NCCO (x = 0.15).Comment: to be published in Physica C (Proceedings of ISS2003

Substitution for Cu in the electron-doped infinite-layer superconductor Sr0.9La0.1CuO2, Ni reduces Tc much faster than Zn

We report on the effect of substitution for Cu on Tc of electron-doped infinite-layer superconductors Sr0.9La0.1Cu1-xRxO2, R = Zn and Ni. We found that Tc was nearly constant until x = 0.03 for R = Zn, while superconductivity was nearly suppressed for x = 0.02 with dTc/dx = 20 K/% for R = Ni. This behavior is very similar to that of conventional superconductors. These findings are discussed in terms of the superconducting gap symmetry in the cuprate superconductors including another electron-doped superconductor, (Nd,Ce)2CuO4-y.Comment: 5 pages and 2 EPS figures, [email protected] for material reques

Room Temperature Copper(II)-Catalyzed Oxidative Cyclization of Enamides to 2,5-Disubstituted Oxazoles via Vinylic C–H Functionalization

A copper(II)-catalyzed oxidative cyclization of enamides to oxazoles via vinylic C–H bond functionalization at room temperature is described. Various 2,5-disubstituted oxazoles bearing aryl, vinyl, alkyl, and heteroaryl substituents could be synthesized in moderate to high yields. This reaction protocol is complementary to our previously reported iodine-mediated cyclization of enamides to afford 2,4,5-trisubstituted oxazoles.National Institutes of Health (U.S.) (Grant GM58160