THE VAN HOVE SINGULARITY IN HIGH T<sub>c</sub> SUPERCONDUCTORS

Horbach, M. L.; Kajüter, H.

doi:10.1142/s0217979295000434

Cited by 6 publications

(6 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…formula(3) in powers of the voltage, we derived an approximate expression for the conductance of a symmetrical junction with a rectangular barrier = and the same Fermi energies in both electrodes EF1= EF,conductance coincides with the respective formula reported by Brinkman et a!.…”

supporting

confidence: 81%

<title>Tunneling conductance of metaloxide junctions</title>

Svistunov¹,

Khachaturov²,

Belogolovskii³

1996

SPIE Proceedings

View full text Add to dashboard Cite

The differential conductance behavior of metallinsulator/metaloxjde and metaloxide/insulator/metaloxide tunnel structures has been studied. It is found that because of small Fermi energies of metaloxides a number of universally accepted principles of tunneling spectroscopy of conventional materials cease to be valid. First, the shape of tunneling characteristics of a metaloxide is unusually sensible to barrier parameters: the thickness of the insulating layer and the barrier height. If the barrier height is quite large or the thickness is small the dependence of tunnel conductance on voltage for a metaloxide/insulator/metaloxide structure manifests a zero-bias "peak resistance" anomaly. On further increasing the height or decreasing the thickness the dependence of conductance versus voltage V decreases throughout the entire range of voltages. Second, the parabola-like dependence of r(V) for a metallinsulator/metaloxide structure calculated for a symmetrical rectangular potential barrier appears not to be symmetrical. Its minimum occurs at a finite voltage. Finally, in contrast to metal/oxide/metal contacts the metaloxide tunnel characteristics calculated in the WKB-approximation differ considerably from the corresponding ones obtained in the "sharp boundaries" model.

show abstract

supporting

confidence: 81%

<title>Tunneling conductance of metaloxide junctions</title>

Svistunov¹,

Khachaturov²,

Belogolovskii³

1996

SPIE Proceedings

View full text Add to dashboard Cite

show abstract

“…At present there is no consensus on the mechanism of such high-T c superconductivity. 18,51,97,210,211 In the last years, the role of the van Hove singularity in the increasing of T c are often discussed. 97 70 Here guide to search must be the phase diagrams presented in Fig.…”

Section: Possible Keys To High-t C Critical Magnetic Field and Currentmentioning

confidence: 99%

“…,210 However, many experimental results show97,210,212 that the van Hove singularity is neither a necessary nor a sufficient condition for high-T c values. Here we indicate a more real possibility of the increasing of T c , H c1 , H c2 and J c within the predictions 70 and present theory.…”

mentioning

confidence: 99%

The Microscopic Theory of Superfluidity and Superconductivity Driven by Single Particle and Pair Condensation of Attracting Bosons

Dzhumanov

1998

Int. J. Mod. Phys. B

View full text Add to dashboard Cite

A original microscopic theory of superfluidity and superconductivity driven by the single particle (SPC) and pair condensation (PC) of attracting bosons both in Fermi and in Bose systems is developed. This theory (as distinct from the existing theories) for Fermi systems contains two order parameters ∆ F and ∆ B characterizing the attracting fermion pairs and boson pairs, respectively. In such systems superconducting (SC) phase transition is accompanied, as a rule, by the formation of k-space composite bosons (e.g. Cooper pairs and bipolarons) with their subsequent transition to the superfluid (SF) state by attractive SPC and PC. A novel Fermi-liquid and SF Bose-liquid theories are elaborated for description this two-stage Fermi-Bose-liquid (FBL) scenario of SC (or SF) transition. The crossover from k-to real (r)-space pairing regime for BCS-like coupling constants γ F 0.7 − 0.9 and the irrelevance of r-space pairs to the superconductivity are shown. The developed SF Bose-liquid theory predicts the first-order phase transition SPC ↔ PC of attracting 3d-bosons with the kink-like behaviors of all SC (SF) parameters near T = T * B < Tc in accordance with the observations in 4 He, 3 He and superconductors. It is argued that the coexistence of the order parameters ∆ F and ∆ B leads to the superconductivity by two FBL scenarios. One of these scenarios is realized in the so-called fermion (type I, II and III) superconductors (FSC) (where formation of k-space composite bosons and their condensation occur at the same temperature) and the other in the boson (type II and III) superconductors (BSC) (where BCS-like pairing take place in the normal state with manifesting of the second-order phase transition and opening of the pseudogap at T = T F > Tc). There the gapless superfluidity (superconductivity) is caused by the gapless excitation spectrum of bosons at T ≤ T * B and not by the presence of point or line nodes of the BCS-like gap ∆ F assumed in some s-, pand d-pairing models. The 3D-and 2D-insulator-metal-superconductor phase diagrams are presented. The necessary and sufficient microscopic criterions for superfluidity is formulated. The theory proposed are in close agreement with the observations in 4 He, 3 He, superconductors, nuclear and neutron star matter, cosmology, etc.

show abstract

“…The physical consequences of the presence of a small energy scaleμ − ǫ vHs have been discussed in the literature in great detail [21].…”

mentioning

confidence: 99%

“…We will consider the ∆ (0) vs. n 0 plane for two qualitatively different cases, t pp < t 0 and t pp > t 0 , where where n vHs is the value of filling corresponding to μ = ǫ vHs . The physical consequences of the presence of a small energy scale μ − ǫ vHs have been discussed in the literature in great detail [21].…”

mentioning

confidence: 99%

Band crossing and novel low-energy behaviour in a mean field theory of a three-band model on a Cu - O lattice

Golosov¹,

Ruckenstein²,

Horbach³

1998

J. Phys.: Condens. Matter

View full text Add to dashboard Cite

We study correlation effects in a three-band extended Hubbard model of Cu-O planes within the 1/N mean field approach, in the infinite U limit. We investigate the emerging phase diagram and discuss the low energy scales associated with each region. With increasing direct overlap between oxygen orbitals, t pp > 0, the solution displays a band crossing which, for an extended range of parameters, lies close to the Fermi level. In turn this leads to the nearly nested character of the Fermi surface and the resulting linear temperature dependence of the quasi-particle relaxation rate for sufficiently large T . We also discuss the effect of band crossing on the optical conductivity and comment on the possible experimental relevance of our findings.

show abstract

THE VAN HOVE SINGULARITY IN HIGH T_c SUPERCONDUCTORS

Cited by 6 publications

References 0 publications

<title>Tunneling conductance of metaloxide junctions</title>

<title>Tunneling conductance of metaloxide junctions</title>

The Microscopic Theory of Superfluidity and Superconductivity Driven by Single Particle and Pair Condensation of Attracting Bosons

Band crossing and novel low-energy behaviour in a mean field theory of a three-band model on a Cu - O lattice

Contact Info

Product

Resources

About

THE VAN HOVE SINGULARITY IN HIGH Tc SUPERCONDUCTORS

Cited by 6 publications

References 0 publications

<title>Tunneling conductance of metaloxide junctions</title>

<title>Tunneling conductance of metaloxide junctions</title>

The Microscopic Theory of Superfluidity and Superconductivity Driven by Single Particle and Pair Condensation of Attracting Bosons

Band crossing and novel low-energy behaviour in a mean field theory of a three-band model on a Cu - O lattice

Contact Info

Product

Resources

About

THE VAN HOVE SINGULARITY IN HIGH T_c SUPERCONDUCTORS