Tunneling spectroscopy of various underdoped Bi2Sr2CaCu2O8+δ (original) (raw)

First Scanning Tunnelling Spectroscopy on Bi2Sr2Ca2Cu3O10 (Bi2223) single crystals

2005

We report the first low temperature scanning tunnelling microscopy and spectroscopy study of high quality Bi2223 crystals. We present atomic resolution and show spectroscopic data acquired on two different samples. In one case, for Tc= 109K and a transition width of only 1K, we obtained an extremely homogeneous sample with a gap value of 60 meV over at least 50 nm. In the other case, the respective parameters were Tc= 111K with a transition width of 1.7K and yielded a slightly less homogeneous sample with a gap of 45 meV. We evidence strong similarities with Bi2Sr2CaCu2O8 (Bi2212) and discuss the doping level of our samples.

Oxygen doping and temperature dependence of the tunneling spectroscopy on Bi2Sr2CaCu2O8+?

Journal of Low Temperature Physics, 1996

We present local probe tunneling spectroscopy of Bi2Sr2CaCu2Os+ 6 single crystals for different oxygen concentrations, from optimally doped (Tc=92.2 K) to highly overdoped (Tc=56.0 K) phases. With increasing oxygen overdoping, the superconducting gap (Ap) is reduced and the dip structure beyond Ap at negative sample bias ! shifts toward the Fermi energy. Apart from the shift in energy of these features, the generic shape of the tunneling spectra remains unchanged. The gap roughly scales with T c, and 2Ap/kBT c stays large even in the highly overdoped phase. We also present preliminary results on the temperature dependence of the tunneling spectra. They are consistent with a gap that is largely independent on temperature up to the vicinity oft c.

Scanning tunneling spectroscopy on Bi2Sr2Ca2Cu3O10+δ single crystals

Journal of Physics and Chemistry of Solids, 2006

We report the first low temperature scanning tunnelling microscopy and spectroscopy study of high quality Bi 2 Sr 2 Ca 2 Cu 3 O 10+δ crystals. We present atomic resolution and show spectroscopic data acquired on two different samples. In one case, for T c = 109 K and a transition width of only 1 K, we obtained an extremely homogeneous sample with ∆ p = 60 meV over at least 50 nm. In the other case, the respective parameters were T c = 111 K and ∆T c = 1.7 K and yielded a slightly less homogeneous sample with ∆ p = 45 meV. We evidence strong similarities with Bi 2 Sr 2 CaCu 2 O 8+δ and discuss the doping level of our samples.

Break junction tunnelling on Bi2Sr2CaCu2O8+?-single crystals

Zeitschrift f�r Physik B Condensed Matter, 1992

Break junction tunnelling experiments on Bi2Sr2Ca-Cu20 s +o-single crystals were performed at different temperatures. Carefully adjusted samples exhibited conductance curves showing only one large peak at positive and negative bias voltages. From these measurements a gap value A=(21.2_2.8)meV, i.e. 2A/kBTc=(5.5+_0.8), was inferred. The behaviour of the conductance curves is similar to that of conventional superconductors but with a much larger broadening of the tunnelling characteristic. Therefore, several models which could explain this smearing are compared with the experimental data. However, it is found that none of them is capable of fitting the conductance curves convincingly. In some cases tunnel characteristics similar to those predicted by a charging effect model or a multigap model were obtained.

Bi2Sr2CaCu2O8+x Single Crystals Probed by c-Axis Tunneling Measurements

1998

We fabricated small-size stacks on the surface of Bi2Sr2CaCu2O8+x (BSCCO-2212) single crystals with the bulk transition temperature Tc≃90 K, each containing a few intrinsic Josephson junctions. Below a critical temperature T ′ c ( ≪ Tc), we have observed a weakened Josephson coupling between the CuO2 superconducting double layer at the crystal surface and the adjacent one located deeper inside a stack. The quasiparticle branch in the IV data of the weakened Josephson junction (WJJ) fits well to the tunneling characteristics of a d-wave superconductor ( ′)/insulator/d-wave superconductor (D ′ ID) junction. Also, the tunneling resistance in the range T ′ c<T<Tc agrees well with the tunneling in a normal metal/insulator/d-wave superconductor (NID) junction. In spite of the suppressed superconductivity at the surface layer the symmetry of the order parameter appears to remain unaffected. I.

Microscopic modeling of tunneling spectra in Bi$_2$Sr$_2$Ca$_2$Cu$_3$O$_{10+\delta}$ (Bi-2223)

arXiv (Cornell University), 2013

We study a series of spectra measured in the superconducting state of optimally-doped Bi-2223 by scanning-tunneling spectroscopy. Each spectrum, as well as the average of spectra presenting the same gap, is fit using a microscopic model that takes into account the band structure, the BCS gap, and the interaction of electrons with the spin-resonance mode. After describing our measurements and the main characteristics of the strong-coupling model, we report the whole set of parameters determined from the fits, and we discuss trends as a function of the gap magnitude. We also simulate angle-resolved photoemission spectra using the parameters resulting from our fits, and compare with recent experimental data.

Temperature dependence of tunneling spectra in YBa2Cu3O7−δ and Bi2Sr2CaCu2O8+δ single crystals

Journal of Electron Spectroscopy and Related Phenomena, 2000

During past years, scanning tunneling spectroscopy (STS) investigations of high temperature superconductors have revealed unusual characteristics of the superconducting gap. We present here the temperature dependence of the tunneling conductance spectra on YBa Cu O and Bi Sr CaCu O single crystals. We discuss similarities and differences 2 3 7 2d 2 2 2 81d between these two compounds. In particular we note that while in Bi Sr CaCu O a pseudogap is observed above the 2 2 2 81d critical temperature, even in overdoped samples, we find no indication of a pseudogap in optimally doped YBa Cu O 2 3 7 2d above T. This is consistent with other striking differences between the two systems and supports the interpretation of the c pseudogap in terms of strong superconducting correlations.

PSEUDO-GAP FEATURES OF INTRINSIC TUNNELING IN (HgBr 2 )-Bi2212 SINGLE CRYSTALS

International Journal of Modern Physics B, 1999

The c-axis tunneling properties of both pristine Bi2212 and its HgBr 2 intercalate have been measured in the temperature range 4.2-250 K. Lithographically patterned 7-10 unit-cell heigh mesa structures on the surfaces of these single crystals were investigated. Clear SIS-like tunneling curves for current applied in the c-axis direction have been observed. The dynamic conductance d I/ d V(V) shows both sharp peaks corresponding to a superconducting gap edge and a dip feature beyond the gap, followed by a wide maximum, which persists up to a room temperature. Shape of the temperature dependence of the c-axis resistance does not change after the intercalation suggesting that a coupling between CuO 2-bilayers has little effect on the pseudogap.

Tunneling studies on single crystals of superconducting Bi2Ca1−xYxSr2Cu2O8+δ

Physica C: Superconductivity, 1992

Tunneling studies have been carried out on single crystals of Bi>Ca, ,Sr,Cu& x+,> over a wide range of compositions wherein the hole concentration varies by a factor of 2.5. The 23 value varies between 25 meV and 75 meV over the composition range studied, but scales with 2A/k,T,=9.5 throughout