scholarly journals Coexistence of the superconducting energy gap and pseudogap above and below the transition temperature of cuprate superconductors

2013 ◽  
Vol 87 (14) ◽  
Author(s):  
J. L. Tallon ◽  
F. Barber ◽  
J. G. Storey ◽  
J. W. Loram
Keyword(s):  
Transition Temperature ◽  
Cuprate Superconductors ◽  
Energy Gap ◽  
Superconducting Energy Gap

Unrelated BCS-like pairing pseudogap and critical superconducting transition temperature in various cuprate compounds

2018 ◽  
Vol 32 (18) ◽  
pp. 1850195
Author(s):  
S. Dzhumanov ◽  
E. X. Karimboev ◽  
Sh. S. Djumanov
Keyword(s):  
Transition Temperature ◽  
Superconducting Transition Temperature ◽  
Order Parameter ◽  
Cuprate Superconductors ◽  
Energy Gap ◽  
Characteristic Temperature ◽  
Superconducting Order Parameter ◽  
Superconducting Transition ◽  
Gap Formation ◽  
Arpes Data

The smooth evolution of the energy gap observed in the tunneling and angle-resolved photoemission spectra (ARPES) of high-[Formula: see text] cuprates with lowering the temperature from a pseudogap state above the critical temperature [Formula: see text] to a superconducting state below [Formula: see text], has been poorly interpreted as the evidence that the pseudogap must have the same origin as the superconducting order parameter, and therefore, must be related to [Formula: see text]. We argue that such an explanation of the tunneling gap and ARPES data is misleading. We show that the BCS-like energy gap (or pseudogap) opening in the electronic excitation spectrum of underdoped-to-overdoped cuprates at a characteristic temperature [Formula: see text] and the true superconducting order parameter appearing only at [Formula: see text] are unrelated. The superconducting phenomenon in unconventional cuprate superconductors is fundamentally different from the BCS-like pairing of fermionic quasiparticles, and the superconducting transition temperature [Formula: see text] is not determined by the BCS-like gap formation. The unusual superconducting order parameter in these high-[Formula: see text] materials appears at [Formula: see text] and coexists with the BCS-like gap (or pseudogap) below [Formula: see text].

MERCURY-BASED SUPERCONDUCTORS WITH QUASI-NORMAL OCCUPANCY

1995 ◽  
Vol 09 (18) ◽  
pp. 1175-1184
Author(s):  
M. MORENO ◽  
R.M. MÉNDEZ-MORENO ◽  
S. OROZCO ◽  
M.A. ORTÍZ
Keyword(s):  
Transition Temperature ◽  
Fermi Surface ◽  
Weak Coupling ◽  
Cuprate Superconductors ◽  
Energy Gap ◽  
Oxide Superconductors ◽  
Coupling Constant ◽  
Effective Coupling ◽  
Small Energy ◽  
Copper Oxide Superconductors

A model with anomalous occupancy is applied to Hg-based cuprate superconductors. The anomaly consists of a small energy gap near the Fermi surface, the scale of the gap anomaly is of order of the cutoff (v.g. Debye) energy. Values of the anomalous occupancy parameters for Hg-based superconductors are obtained for different values of the ratio R and the effective coupling constant, within the weak coupling. As these materials have the highest transition temperature known for layered copper-oxide superconductors, they serve as a new testing ground for various proposed models.

scholarly journals Effect of Multiple Orders on Superconducting Transition Temperature of Hole Doped Cuprates

2017 ◽  
Vol 9 (4) ◽  
pp. 341-349
Author(s):  
I. Qabid ◽  
S. H. Naqib
Keyword(s):  
Transition Temperature ◽  
Superconducting Transition Temperature ◽  
Cuprate Superconductors ◽  
Energy Gap ◽  
Density Wave ◽  
Spin Density Wave ◽  
Superconducting Transition ◽  
Electronic Density ◽  
Special Cases ◽  
Multiple Orders

Hole doped high-Tc cuprate superconductors are strongly correlated electronic systems. In these materials, various electronic orders are often found, but whether they support or compete with superconducting order is not unambiguous. Superconductivity normally manifests itself by a superconducting gap in the electronic density of states (EDOS). In cuprates, a gap appears even in the normal state called the pseudogap (PG). For certain doping range, spin density wave and charge density wave coexist with superconductivity by inducing corresponding additional gaps in the EDOS. In this study, we have tried to obtain expression for superconducting transition temperature, Tc by solving the BCS (Bardeen-Cooper-Schrieffer) energy gap equation in the presence of depleted EDOS of various origins and types. We have been successful to solve the weak-coupling BCS integral equation analytically in some special cases and also in the general case by using numerical integration. We have found that depending on conditions these non-pairing gaps/orders can enhance as well as reduce Tc.

ELECTRON TUNNELING MEASUREMENTS OF ENERGY GAP IN SUPERCONDUCTORS YBaCuO, LaSrCuO AND BPBO

1987 ◽  
Vol 01 (02) ◽  
pp. 555-559 ◽  
Author(s):  
Hongjie TAO ◽  
Yingfei CHEN ◽  
Li LU ◽  
Qiansheng YANG ◽  
Bairu ZHAO ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Strong Coupling ◽  
Perovskite Structure ◽  
Energy Gap ◽  
Electron Tunneling ◽  
Point Contact ◽  
Tunneling Conductance ◽  
Temperature Ratio ◽  
Superconducting Energy Gap

We have carried out superconducting energy gap measurements for polycrystalline perovskite-structure superconductors YBaCuO, LaSrCuO and BPBO with point contact tunneling. The tunneling conductance curves for YBaCuO, LaSrCuO and BPBO show the energy gap to transition temperature ratio 2Δ/kTc =4.7, 7.8 and 5.05 respectively, which is consistant with the strong-coupling superconductivity.

Low energy impurity kink in the normal and anomalous self-energies in Bi-cuprate superconductors

2015 ◽  
Vol 29 (25n26) ◽  
pp. 1542005
Author(s):  
Jin Mo Bok ◽  
Jong Ju Bae ◽  
Seung Hwan Hong ◽  
X. J. Zhou ◽  
Han-Yong Choi
Keyword(s):  
Cuprate Superconductors ◽  
Energy Analysis ◽  
Energy Gap ◽  
Low Energy ◽  
The Self ◽  
Energy Term ◽  
Impurity Effects ◽  
Self Energy ◽  
Superconducting Energy Gap ◽  
Arpes Data

The sharp low energy kink (LEK) in quasiparticle (qp) spectra well below the superconducting energy gap observed in the angle-resolved photo-emission spectroscopy (ARPES) of the Bi-cuprates may be understood in terms of the forward scattering impurities located off the Cu–O planes. The relevance of the idea has been established by comparing the calculated normal self-energy from the off-plane impurity effects and the extracted one from the self-energy analysis of [Formula: see text] (Bi2212) ARPES data in Hong et al. [Phys. Rev. Lett. 113, 057001 (2014)]. In addition to the explanation of the LEK, this is a necessary step to analyze ARPES data, to reveal the spectrum of fluctuations promoting superconductivity. We also present the extracted anomalous self-energy from the self-energy analysis, which is its first experimental determination as far as we are aware of. The extracted anomalous self-energy and its implications are discussed in comparison with the calculated impurity self-energy term.

Superconductivity of very thin aluminium films

1968 ◽  
Vol 46 (9) ◽  
pp. 1129-1132 ◽  
Author(s):  
D. G. Walmsley ◽  
C. K. Campbell ◽  
R. C. Dynes
Keyword(s):  
Transition Temperature ◽  
Temperature Dependence ◽  
Crystallite Size ◽  
Energy Gap ◽  
Superconducting Energy Gap

This note presents the results of superconductive tunneling measurements which show that very thin (50–100 Å) aluminium films exhibit a unique superconducting energy gap. The temperature dependence of this gap is BCS-like, and the ratio of the gap magnitude—as extrapolated to T = 0 °K (2Δ(0))—to the observed transition temperature, Tc, remains close to the usual BCS value of 3.52 k. The effect of crystallite size on deviations from BCS results is also discussed in relation to experimental observations.

Superconducting energy gap of NbS2

1984 ◽  
Vol 62 (8) ◽  
pp. 776-779 ◽  
Author(s):  
R. J. Kennedy ◽  
B. P. Clayman
Keyword(s):  
Magnetic Susceptibility ◽  
Transition Temperature ◽  
Energy Gap ◽  
Far Infrared ◽  
The Novel ◽  
Superconducting Transition ◽  
Small Particles ◽  
Energy Gaps ◽  
Superconducting Energy Gap ◽  
Novel Method

The superconducting energy gaps of small particles (1–10 μm) of 2H–NbS2 and 2H–NbSe2 have been measured by far-infrared (FIR) transmission spectroscopy. Comparison of these results with previous FIR measurements made on millimetre-size single crystals of 2H–NbSe2 validates the use of the novel method of sample preparation used here. Comparison of the gap frequencies (νg) with the superconducting transition temperature (Tc) determined by magnetic susceptibility measurements indicates that 2H–NbS2, unlike 2H–NbSe2, exhibits non-Bardeen–Cooper–Schrieffer (BCS)-like behaviour, with hνg/kTc = 2.3.

scholarly journals Phonon self-energy effects in the superconducting energy gap ofMgB2point-contact spectra

2004 ◽  
Vol 69 (10) ◽  
Author(s):  
I. K. Yanson ◽  
S. I. Beloborod’ko ◽  
Yu. G. Naidyuk ◽  
O. V. Dolgov ◽  
A. A. Golubov
Keyword(s):  
Energy Gap ◽  
Self Energy ◽  
Superconducting Energy Gap
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