Observation of gap anisotropy in YBa2Cu3O7−δ by tunneling

doi:10.1016/0921-4534(88)90333-4

Physica C: Superconductivity

Volumes 153–155, Part 3, June 1988, Pages 1385-1386

https://doi.org/10.1016/0921-4534(88)90333-4 Get rights and content

Abstract

Superconductive energy gap of YBa₂Cu₃O_7−δ are measured in anovel broken film edge junction. (001), (103) and (110) oriented films are broken in a cryogenic environment along the appropriate directions together with the SrTiO₃ substrate. Pb electrode is brought close in situ to the clean broken film edge. The normalized energy gap 2Δ(0)/k_BT_c measured in the direction along and perpendicular to the Cu-O plane are found to be 5.9±0.2 and 3.6±0.2 respectively. These values are independent of the variation in the values of T_c within the examined range of 40K∽90K.

Reference (10)

WorthingtonT.K. et al.
Phys. Rev. Lett.
(1987)
EnomotoY. et al.
Jpn. J. Appl. Phys.
(1987)
EbisawaH. et al.
Jpn. J. Appl. Phys.
(1987)
KirtleyJ.R. et al.
Phys. Rev.
(1987)
SchlesingerZ. et al.
Phys. Rev. Lett.
(1987)
FujitaJ. et al.

There are more references available in the full text version of this article.

Cited by (60)

Hydrodynamic formulation of scale relativity theory and unified superconductivity by means of a fractal string
2003, Physica C: Superconductivity and its Applications
Citation Excerpt :
Notice that in Ref. [44] 2Ec(0)/kBTc=3.8±0.2 and 2Eab(0)/kBTc=5.8±0.2, or in Ref. [45] 2Ec(0)/kBTc=3.6±0.2 and 2Eab(0)/kBTc=5.9±0.2.
In the frame of hydrodynamic formulation of scale relativity theory for a coherent quantum fluid, one shows that some parameters of high-temperature superconductors (critical field, critical current, pair breaking time, fluxoid, state density, gap energy, etc.) come from the non-differentiability of the quantum space–time. Then, the vortex streets (responsible for superconductivity by means of the in-phase lattice oscillations mechanism) and the anyons (responsible for superconductivity by means of the composite fermions mechanism) may be considered as two-dimensional projections of a higher-dimensional fractal string, which implies the existence of just one mechanism inducing type II superconductivity.
Cantorian ε<sup>(∞)</sup> space-time, a hydrodynamical model and unified superconductivity
2003, Chaos, Solitons and Fractals
We prove that the fractal space-time interpretation of Nelson’s stochastic quantum mechanics may be put into a one-to-one correspondence to the hydrodynamic model of quantum mechanics. Some implications of this correspondence are analyzed: Navier–Stokes type equations, uncertainty relation and type II superconductivity by means of a higher-dimensional fractal string. The two-dimensional (2D) projections of the higher fractal string corresponds to the anyons and 1D projections to the Cooper pair. The Cantorian-fractal structures occur, either by assimilating the Cooper pair with a two coupled oscillators (a simple mechanical model for ε^(∞) theory), or by El Naschie’s filling factor ν≡φ³=0.23606 (Cantorian-fractal quantum Hall effect).
The Cantorian structure of the background magnetic field and high temperature superconductors
2000, Chaos, Solitons and Fractals
One builds the solution of GL equation in terms of the elliptic cn function of complex argument. The real part of the complex action, $S =ℏ ln cn (u)$ , corresponds to the potential of a vortex lattice, and from here, through the elliptic function degeneration, to the vortex streets. Considering the vortex streets fixed on vacuum by a background magnetic field through pinning, from equating the current density to zero one determines the field structure: the mean value will be roughly equal to B_C₂, and its flux will be fractional. The fractional flux will be associated to quasi-particles obeying the ‘anyonic’ statistics. At low temperatures and high external magnetic field, the structure of background field will be of Cantorian type.
The superconducting ratio 2Δ T<inf>c</inf> and its dependence with T<inf>c</inf> in the infinite-range hopping approach to the negative-U Hubbard model
1995, Solid State Communications
On the BCS theory of superconductivity in systems with overlapping bands II. Overlap, hybridisation, antiferromagnetism, charge transfer, and symmetry shifts in high-T<inf>c</inf> cuprates
1995, Physica C: Superconductivity and its Applications
A mean-field (MF) theory is proposed in the Green's function method of paper I which, in the same scheme, accounts for antiferromagnetism (AF), charge transfer (CT), and superconductivity (SC) in d-p cuprates. The AF, dominant in the narrow-bandwidth regime, is determined by level separation. This gives way to a broad-bandwidth CT state which spills over and cooperates with SC, resulting in high T_c. Our spinor representation of the pairing t-model (PtM) allows, for easy understanding of the gradual evolution of states, on the basis of simple energy symmetry. PtM energy profiles are exhibited and reproduce results from other MF models as limiting cases. The SC is foreshadowed by level equalisation, strong vibronic admixing, and anti-adiabatics that manifest, in the quasiparticle spectrum, the Jahn-Teller effect. The latter is observed as an orthorhombic ⇔ tetragonal transition in the cuprates. Modelling high-T_c. SC on CT-renormalised phonon (ion plasma) modes, reproduces the experimental T_c for most known cuprates. We believe that the present theory embodies novel solutions to the basic problems of normal and SC cuprates, in the simple Bardeen-Cooper-Schrieffer (BCS)-type model.
Plasmons below T<inf>c</inf> in cuprate superconductors
1994, Physica C: Superconductivity and its applications
We used the layered electron gas model to perform a theoretical study of frequency and line shape for plasmons below T_c in cuprate superconductors, in the frequency range $h ̵$ ω≤2Δ≤qv_F<k_BT<k_BT_c, where q, Δ, v_F, k_B and T are the component of the wave vector in the a-b-plane, the binding energy of a Cooper pair, Fermi velocity, Boltzmann constant and the temperature, respectively. The polarizability for a two-dimensional plane, which corresponds to a conducting Cu-O plane, is calculated for the above-mentioned ω-range. The calculated polarizability is then used to calculate the imaginary part of the inverse dielectric response function, which gives rise to the frequency and line shape of plasmons. The calculated plasmon frequencies and the line shapes are found to be of similar nature to that of a three-dimensional electron gas below T_c.

View all citing articles on Scopus

View full text

Observation of gap anisotropy in YBa2Cu3O7−δ by tunneling

Abstract

Phys. Rev. Lett.

Jpn. J. Appl. Phys.

Jpn. J. Appl. Phys.

Phys. Rev.

Phys. Rev. Lett.

Observation of gap anisotropy in YBa₂Cu₃O_7−δ by tunneling