Physics / Fizik
Permanent URI for this collectionhttps://hdl.handle.net/11147/6
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Article Citation - WoS: 16Citation - Scopus: 18Tunneling Studies of Multilayered Superconducting Cuprate (cu,c)ba2ca3cu4o12+?(World Scientific Publishing Co. Pte Ltd, 2003) Miyakawa, Nobuaki; Tokiwa, K.; Mikusu, S.; Zasadzinski, John F.; Özyüzer, Lütfi; İshihara, T.; Kaneko, Tsutomu; Watanabe, T.; Gray, Kenneth E.Point contact tunneling data are reported in a multilayered high-T c cuprate (Cu,C)Ba2Ca3Cu4O 12+δ with Tc = 117 K. The tunneling spectra in the superconducting state (T ≪ Tc) display spectral features such as well-defined superconducting gap peak at ±Δ as well as dip-hump structures beyond the peaks. In some cases, the spectra with two-gaps have been observed, indicating the coexistence of two inequivalent superconducting layers. The statistical distribution of superconducting gap magnitude suggests two distinct kinds of superconducting gaps that may originate from two inequivalent CuO2 planes, a characteristics of multilayered cuprates with n ≥ 3.Article Citation - WoS: 2Citation - Scopus: 2The Icrn Value in Intrinsic Josephson Tunnel Junctions in Bi2sr2cacu2o8+? (bi2212) Mesas(Springer Verlag, 2011) Kurter, Cihan; Özyüzer, Lütfi; Hinks, David G.; Gray, Kenneth E.; Zasadzinski, John F.The c-axis current-voltage I(V) characteristics have been obtained on a set of mesas of varying height sculpted on Bi2Sr2CaCu2O8+δ (Bi2212) crystals intercalated with HgB2. The intercalation, along with the small number of junctions in the mesa, N = 6–30, minimizes the degree of self-heating, leading to a consistent Josephson critical current, IC, among junctions in the mesa. The Bi2212 crystals with a bulk TC =74 K are overdoped and display negligible pseudogap effects allowing an accurate measure of the normal state resistance, RN. These properties make themesas nearlyideal for the determinationof the Josephson ICRN product.Wefind ICRN valuesconsistently ∼30% of the quasiparticle gap parameter, /e, which was measured independently using a mechanical contact, break junction technique. The latter was necessitated by higher bias heating effects in the mesas which prevented direct measurements of the superconducting gap. These values are among the highest reported and may represent the maximum intrinsic value for ICRN. The results indicate that the c-axis transport is a mixture of coherent and incoherent tunneling.Article Citation - WoS: 31Citation - Scopus: 30Absence of Pseudogap in Heavily Overdoped Bi2sr2cacu2o8+? From Tunneling Spectroscopy of Break Junctions(Institute of Physics Publishing, 2002) Özyüzer, Lütfi; Zasadzinski, John F.; Gray, Kenneth E.; Kendziora, Christopher A.; Miyakawa, NobuakiWe report tunneling spectroscopy of superconductor-insulator-superconductor break junctions on heavily overdoped Bi2Sr2CaCu2O8+δ with Tc = 56 K. At T ≪ Tc, the junction conductances display well-defined quasiparticle peaks at ±2Δ and in some cases a Josephson current at zero bias. Gap values as small as Δ = 10.5 meV have been observed leading to 2Δ/kTc near the BCS limit for dx2-y2 pairing. Temperature dependence of the gap magnitude, Δ(T), follows the BCS relation and both the quasiparticle gap and Josephson current vanish for T > Tc. Above Tc, the tunneling conductance shows a flat background without any indication of a pseudogap near the Fermi level.Article Citation - WoS: 1Citation - Scopus: 1Modification of Al-Oxide Tunnel Barriers With Organic Self-Assembled Monolayers(American Institute of Physics, 1999) Okur, Salih; Zasadzinski, John F.Al-oxide tunneling barriers were modified by exposure to a vapor of n-octadecyltrimethoxysilane which forms self-assembled monolayers. The dynamic conductance dI/dV of the modified Al-oxide barrier between Al and Pb electrodes was measured at 4.2 K. Quasilinear conductance backgrounds are observed up to 200 mV with a strength that increases with increasing exposure time from 10 to 60 min. A saturation effect is observed around 200 mV. Beyond 200 mV the dynamic conductance shows a parabolic behavior indicative of elastic tunneling from an asymmetric barrier. The linear background is attributed to inelastic tunneling from a continuum of excitations