Doping Dependence on Two Sizes of Superconducting Gaps on Tl1223 by Tunneling Spectroscopy at 4.2K

AbstractWe present tunneling results on tri-layered cuprate superconductors TlBa2Ca2Cu3O8.5+δ (Tl1223) with two different hole concentration, which are an over-doped Tl1223 with TC ∼ 112K (OD-112K) and a slightly over-doped Tl1223 with TC ∼ 126K (SOD-126K). The tunneling conductances on both samples exhibited two sizes of gaps originated from outer (OP) and inner (IP) CuO2 planes. The superconducting gap at each planes, Δ(OP)/e ≈ Vp(OP) and Δ(IP)/e ≈ Vp(IP) on OD-112K are observed that Vp(OP) is 22 ± 2mV and Vp(IP) is 37 ± 4mV. Similarly, Vp(OP) is 26 ± 2mV and Vp(IP) is 39 ± 3mV on SOD-126K. Although both Vp(OP) and Vp(IP) decrease with increasing oxygen contents, ΔVp(OP) = Vp(OP)(SOD-126K) - Vp(OP)(OD-112K) is larger than ΔVp(IP) for IP. Moreover, ΔVp(plane) Vp(IP) - Vp(OP) increases with overdoping. These results as a function of doping implies the OP might control the variation of TC dominantly

Tunneling studies of multilayered superconducting cuprate (Cu,C)Ba 2Ca3Cu4O12+δ

4th International Conference on New Theories, Discoveries and Applications of Superconductors and Related MaterialsPoint 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.Japan Society for the Promotion of Science; US-DOE, BES-MS under contract no. W-31-109-ENG-38; TUBITAK TBAG-2031; Turkish Academy of Sciences, Young Scientist Award Program(LO/TUBA-GEBIP/2002-1-17

Atomic-scale spot structures and gap distributions on apical-fluorine cuprate superconductor Ba2Ca5Cu6O12 (O1−x, Fx)2 observed by STM/STS

The atomic-scale surface electronic states on the multi-layered apical-fluorine cuprate superconductor Ba2Ca5Cu6O12 (O1−x, Fx)2 (Tc ≃ 70K) are investigated by using low temperature scanning tunneling microscopy/spectroscopy (STM/STS). The spatial gap distributions show the patch scale of ∼ 0.5 nm, which is quite shorter than the superconducting coherence length ∼ 2-3 nm of other cuprate superconducters of a few nm. The high-bias (∼ 1V) conductance map contains some characteristic spots with contrasts reverse to those at low bias, which are considered to be due to the charge unbalance of apical atoms such as O2− and F−.This research was supported by Grant-in-Aid for Scientific Research (No. 19540370) from JSPS, Japan

Scanning Tunneling Microscopy / Spectroscopy on Multi-Layered Cuprate Superconductor Ba2Ca5Cu6O12 (O1-x Fx)2

Scanning tunneling microscopy/spectroscopy (STM/STS) measurements on multi-layered cuprate superconductor Ba2Ca5Cu6O12 (O 1-x Fx)2 are carried out. STM topographies show randomly distributed bright spot structures with a typical spot size of ~ 0.8 nm. These bright spots are occupied about 28% per one unit cell of c-plane, which is comparable to the regular amount of apical oxygen of 20% obtained from element analysis. Tunneling spectra simultaneously show both the small and the large gap structures. These gap sizes at 4.9 K are about Δ ~ 15 meV and ~ 90 meV, respectively. The small gap structure disappears at the temperature close to TC, while the large gap persists up to ~200 K. Therefore, these features correspond to the superconducting gap and pseudogap, respectively. These facts give evidence for some ordered state with large energy scale even in the superconducting state. For the superconducting gap, the ratio of 2ΔS /KBTC = 4.9 is obtained with TC = 70 K, which is determined from temperature dependence of the tunneling spectra.This research was supported by Grant-in-Aid for Scientific Research (No. 19540370) from JSPS, Japan