Tunneling STM/STS and break-junction spectroscopy of the Pb-doped Bi2223 superconductor (original) (raw)
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Fizika Nizkikh Tempreratur, 2020
Conductance-voltage characteristics (CVCs) of tunnel break junctions made of Bi 2 Sr 2 CaCu 2 O 8+δ crystals were measured. It was demonstrated that the CVCs have a V-shaped inner gap region, similar to those typical of CVCs for tunnel junctions between d-wave superconductors. The CVCs have different forms for different junctions, but all of them reveal weak dip-hump structures outside the inner gap region. Calculations of the tunnel current in the ab plane of the break junctions were carried out in the model of the inhomogeneous d-wave superconductor partially gapped by charge density waves (CDWs). The averaging of the tunnel current over the statistical distributions of both the superconducting and CDW order parameters was carried out. The theoretical results qualitatively reproduce the behavior of experimental curves. A conclusion was made that tunnel direc-tionality and the statistical distributions of both order are crucial factors governing the observed CVC shapes for break junctions made of high-T c oxides.
Physica C: Superconductivity, 2001
From intrinsic tunneling spectroscopy, superconducting-and pseudo-gaps could be separated within a wide range of temperatures. We have found that the two gaps have dierent temperature (T) and magnetic ®eld (H) dependencies. The superconducting gap closes both as T 3 T c and H 3 H c2 , while the pseudo-gap does not change neither with T, or H. This would speak in favor of two coexisting phenomena and against the precursor superconductivity scenario of the pseudo-gap.
TUNNELLING MEASUREMENTS IN THE Bi SUPERCONDUCTORS
Modern Physics Letters B, 1989
Tunnelling experiments made on a crack junction of Bi 2( Sr 0.56 Ca 0.39 Bi 0.05)3 Cu 2 O y show reproducible features in the I-V characteristic. Accurate measurements of the temperature dependence of these features show close agreement with the BCS behavior of the gap. Possible tunnelling processes in this material are discussed in connection with the experimental data.
2008
The tunnel conductance G͑V͒ for break junctions made of single-crystal as-grown Bi 2 Sr 2 CaCu 2 O 8+␦ samples with T c Ϸ 86-89 K were measured and clear-cut dip-hump structures ͑DHSs͒ were found in the range 80-120 mV of the bias voltage V. A theory of tunneling in symmetrical junctions between inhomogeneous charge-density-wave ͑CDW͒ superconductors, considered in the framework of the s-pairing model, has been developed. CDWs have been shown to be responsible for the appearance of the DHS in the tunnel currentvoltage characteristics and properly describe the experimental results.
Low Temperature Physics, 2008
Tunnel conductance G V () for break-junctions made of as-grown single-crystal Bi 2 Sr 2 CaCu 2 O 8+d samples with T c »-86 89 K was measured and clear-cut dip-hump structures (DHSs) were found in the range 80 120-mV of the bias voltage V. The theory of tunneling in symmetric junctions between inhomogeneous charge-density-wave (CDW) superconductors, considered in the framework of the s-pairing model, has been developed. CDWs have been shown to be responsible for the appearance of the DHS in the tunnel current-voltage characteristics and properly describes experimental results.
Physical Review B, 2007
The tunnel conductance G͑V͒ for break junctions made of single-crystal as-grown Bi 2 Sr 2 CaCu 2 O 8+␦ samples with T c Ϸ 86-89 K were measured and clear-cut dip-hump structures ͑DHSs͒ were found in the range 80-120 mV of the bias voltage V. A theory of tunneling in symmetrical junctions between inhomogeneous charge-density-wave ͑CDW͒ superconductors, considered in the framework of the s-pairing model, has been developed. CDWs have been shown to be responsible for the appearance of the DHS in the tunnel currentvoltage characteristics and properly describe the experimental results.
2008
Tunnel conductance G V ( ) for break-junctions made of as-grown single-crystal Bi2Sr2CaCu2O8+ samples with Tc 86 89 K was measured and clear-cut dip-hump structures (DHSs) were found in the range 80 120 mV of the bias voltage V . The theory of tunneling in symmetric junctions between inhomogeneous charge-density-wave (CDW) superconductors, considered in the framework of the s-pairing model, has been developed. CDWs have been shown to be responsible for the appearance of the DHS in the tunnel current-voltage characteristics and properly describes experimental results.
Imaging the Two Gaps of the High-TC Superconductor Pb-Bi2Sr2CuO6+ x
2007
The nature of the pseudogap state, observed above the superconducting transition temperature T C in many high temperature superconductors, is the center of much debate. Recently, this discussion has focused on the number of energy gaps in these materials. Some experiments indicate a single energy gap, implying that the pseudogap is a precursor state. Others indicate two, suggesting that it is a competing or coexisting phase. Here we report on temperature dependent scanning tunneling spectroscopy of Pb-Bi 2 Sr 2 CuO 6+x . We have found a new, narrow, homogeneous gap that vanishes near T C , superimposed on the typically observed, inhomogeneous, broad gap, which is only weakly temperature dependent. These results not only support the two gap picture, but also explain previously troubling differences between scanning tunneling microscopy and other experimental measurements.
Tunneling and infrared spectroscopy on high Tc superconductors
Journal of Physics and Chemistry of Solids, 1993
We have investigated single crystais of Bi$k2Cat,YxC$Oe (x=0 -0.35) by far infrared transmission spectroscopy and by break junction tmmeling. The junctions were made at low temperatures in vacuum, and SIS tunneling was measured at various temperatures and magnetic fields. 'IEe tmmeling resuits are interpreted in terms of a Josephson current and a single electron tunneling density of states (DOS). Although the DOS is found to he zerc at the Fermi level, we do not see a fully developed gap even at temperatures well below the critical temperature.