Sharp gap edge and determination of the fermi velocity in Y1Ba2Cu3O7?? by point contact spectroscopy

Mass, Nir; Ilzycer, D.; Deutscher, G.; Desgardin, G.; Monot, I.; Weger, M.

doi:10.1007/bf00618066

Cited by 47 publications

(10 citation statements)

References 13 publications

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“…10 What was discovered was that for these superconductors the energy scale determined by ASJ reflection is in general different from that obtained from tunneling. More specifically, the ASJ coherence scale follows the same doping dependence as the critical temperature does, while the tunneling gap (or the gap seen by angle resolved photo emission spectroscopy) keeps increasing when the doping is reduced.…”

Section: The Three Experimental Results-a Summarymentioning

confidence: 99%

The role of Cu-O bond length fluctuations in the high temperature superconductivity mechanism

Deutscher¹

2012

Journal of Applied Physics

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High critical current density and its field dependence in mixed rare earth (Nd,Eu,Gd)Ba 2 Cu 3 O 7−δ thin filmsWe review three different kinds of experiments that emphasize the non-BCS, inhomogeneous aspects of superconductivity in the high Tc cuprates. The first is the existence of two different energy scales in the superconducting state, initially identified by a comparison between tunneling and Andreev-Saint-James spectroscopies [Deutscher, Nature (London) 397, 410 (1999)]. The second are EXAFS measurements of the Cu-O bond length distribution, which have shown that below a temperature T* > Tc, it becomes broader than expected from the Debye-Waller broadening and presents a split [Bianconi et al., Phys. Rev. Lett. 76, 3412 (1996)]. The third one is the effect of frozen lattice disorder on critical current and vortex pinning, which profoundly affects the pairing landscape [Gutierrez et al., Nature Mater. 6, 367 (2007)]. We then discuss how these results fit with models in which the electron-lattice interaction plays a leading role. V C 2012 American Institute of Physics. [http://dx.

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Section: The Three Experimental Results-a Summarymentioning

confidence: 99%

The role of Cu-O bond length fluctuations in the high temperature superconductivity mechanism

Deutscher¹

2012

Journal of Applied Physics

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“…The position of the main conductance peak then gives the gap value if, as is now generally believed, it has a d-wave symmetry. The Andreev data were obtained by point contact spectroscopy on a melt textured sample, along the a (or b) axis direction 12 . For these orientations, the return to the normal-state conductance occurs at the gap edge, whether it has s-wave or d-wave symmetry 13 .…”

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confidence: 99%

Coherence and single-particle excitations in the high-temperature superconductors

Deutscher

1999

Nature

351

317

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The 'pseudogap' observed in the electron excitation spectrum of underdoped copper oxide superconductors has become the focus of considerable attention in the field of high-temperature superconductivity. In conventional superconductors, described by 'BCS' theory, an energy gap appears at the superconducting transition temperature (T); the pseudogap, in contrast, is observed well above T (ref. 1) and can be large compared to the conventional BCS gap. Here I compare gap energies, measured by different experimental techniques, for the copper oxide superconductors and show that these reveal the existence of two distinct energy scales: Δ and Δ. The first, determined either by angle-resolved photoemission spectroscopy or by tunnelling, is the single-particle excitation energy-the energy (per particle) required to split the paired charge-carriers that are required for superconductivity. The second energy scale is determined by Andreev reflection experiments, and I associate it with the coherence energy range of the superconducting state-the macroscopic quantum condensate of the paired charges. I find that, in the overdoped regime, Δ and Δ converge to approximately the same value, as would be the case for a BCS superconductor where pairs form and condense simultaneously. But in the underdoped regime, where the pseudogap is observed, the two values diverge and Δ is larger than Δ. Models that may provide a framework for understanding these results involve the existence of pairing above the condensation temperature, as might occur in a crossover from BCS to Bose-Einstein condensation behaviour or from the formation of striped phases.

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“…The materials with a higher energy band gap tend to have the capability of producing smaller constriction sizes. For example YBCO thin film has an out-of-plane energy band gap of 5 meV [10] which allows it to produce nano structures somewhere in the limit of 400 nm. This could be one of the reasons why when the constriction of nano size (394.8 nm) was produced, the walls of the constriction had a tendency to collapse after fabrication.…”

Section: Factors That Limit the Fabrication Of Nanostructuresmentioning

confidence: 99%

Constrictions Fabricated on YBCO Thin Film using the Femtosecond Laser: Limiting Factors

Umenne

2018

Acta Phys. Pol. A

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In this paper we report on the development of a new application of the femtosecond laser, namely, the fabrication of micron, sub-micron and nano sized constrictions on YBCO superconductive thin films. The fabricated micron, sub-micron and nano constrictions have widths of 1.09 µm, 705 nm and 394.8 nm, respectively. The thickness of these constrictions ranged from about 160 nm to 190 nm, as defined by the depth profile on the 3D AFM images. The length of these constrictions ranged from 7.2 µm to 7.5 µm. The length of these constrictions depends on the size of the laser ablation spot used for cutting and on the separation distance between the laser ablation spots along the width of the sample.

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Sharp gap edge and determination of the fermi velocity in Y1Ba2Cu3O7?? by point contact spectroscopy

Cited by 47 publications

References 13 publications

The role of Cu-O bond length fluctuations in the high temperature superconductivity mechanism

The role of Cu-O bond length fluctuations in the high temperature superconductivity mechanism

Coherence and single-particle excitations in the high-temperature superconductors

Constrictions Fabricated on YBCO Thin Film using the Femtosecond Laser: Limiting Factors

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