Physics / Fizik
Permanent URI for this collectionhttps://hdl.handle.net/11147/6
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Article Citation - WoS: 54Citation - Scopus: 55Persistence of Strong Electron Coupling To a Narrow Boson Spectrum in Overdoped Bi2sr2cacu2o8+î Tunneling Data(American Physical Society, 2006) Zasadzinski, John F.; Özyüzer, Lütfi; Coffey, L.; Gray, Kenneth E.; Hinks, David G.; Kendziora, Christopher A.A d-wave, Eliashberg analysis of break-junction and STM tunneling spectra on Bi2Sr2CaCu2O8+Î (Bi2212) reveals that the spectral dip feature is directly linked to strong electronic coupling to a narrow boson spectrum, evidenced by a large peak in I'2F(I). The tunneling dip feature remains robust in the overdoped regime of Bi2212 with bulk Tc values of 56Â Ka62Â K. This is contrary to recent optical conductivity measurements of the self-energy that suggest the narrow boson spectrum disappears in overdoped Bi2212 and therefore cannot be essential for the pairing mechanism. The discrepancy is resolved by considering the way each technique probes the electron self-energy, in particular, the unique sensitivity of tunneling to the off-diagonal or pairing part of the self-energy.Conference Object Citation - WoS: 7Citation - Scopus: 7Aspects of the Tunneling Dip Feature in Bi2sr2cacu2o8+? and Its Relation To the Resonance Spin Excitation(Elsevier Ltd., 2002) Zasadzinski, John F.; Özyüzer, Lütfi; Miyakawa, Nobuaki; Gray, Kenneth E.; Hinks, David G.; Kendziora, Christopher A.Break-junction tunneling data are reported in Bi2Sr2CaCu2O8+δ over a wide range of hole concentration from underdoped to overdoped. The strong conductance peaks in the superconducting state reveal a single gap consistent with d-wave symmetry. In addition, sharp dips are observed at a voltage, Ω/□, measured with respect to the gap edge. These features are shown to be reproduced in other junction types from the literature including atomically resolved STM and □-axis mesas, establishing their intrinsic character. Trends are observed with doping and temperature which link the dip to the resonance spin excitation and indicate that the quasiparticles are strongly coupled to this mode.Article Citation - WoS: 4Citation - Scopus: 4Simultaneous Quasiparticle and Josephson Tunneling in Bscco-2212 Break Junctions(Institute of Electrical and Electronics Engineers Inc., 1999) Özyüzer, Lütfi; Miyakawa, Nobuaki; Zasadzinski, John F.; Yusof, Zikri M.; Romano, Pierom; Kendziora, Christopher A.; Hinks, David G.; Gray, Kenneth E.Tunneling measurements are reported for superconductor-insulator-superconductor (SIS) break junctions on underdoped, optimally-doped, and overdoped single crystals of tSrsCaCiOs-).,! (Bi2212). The junction I -V characteristics exhibit welldefined quasiparticle current jumps at eV = 2A as well as hysteretic Josephson currents. The quasiparticle branch has been analyzed in the framework of dxa_y2 (d-wave) superconductivity and indicates that there is preferential tunneling along the lobe directions of the d-wave gap. For overdoped Bi-2212 with TC-62 K, the Josephson current is measured as a function of junction resistance, Rn, which varied by two orders of magnitude (1 kO to 100 kO). IcRn product is proportional to the 0.47 power of /c and displays a maximum of 7.0 mV. When the hole doping is decreased from overdoped (Tc=62 K) to the underdoped regime (Tc=70 K), the average IcRn product increases as does the quasiparticle gap. The maximum IcRn is ~ 40% of the A/e at each doping level, with a value as high as 25 mV in underdoped Bi-2212.