scholarly journals Vibronic Mechanism of High Tc Superconductivity

2003 ◽  
Vol 17 (18n20) ◽  
pp. 3266-3270 ◽  
Author(s):  
M. Tachiki ◽  
T. Egami ◽  
M. Machida
Keyword(s):  
Transition Temperature ◽  
Order Parameter ◽  
Cuprate Superconductors ◽  
High Temperature Superconductivity ◽  
Attractive Interaction ◽  
Low Frequencies ◽  
High Tc ◽  
Eliashberg Theory ◽  
Bond Stretching ◽  
Vibronic Effect

When phonons strongly mix with electron charge fluctuations with low frequencies, the phonon mediated attractive interaction between electrons is strongly enhanced. The occurrence of the mixing has been indicated by the neutron scattering experimental results that the dispersion of the in-plane Cu–O bond-stretching mode in the high Tc cuprate superconductors is strongly softened near the zone boundary. We propose that the phonon mediated attractive interaction strongly enhanced by the vibronic effect can form a basis for the phonon mechanism of high temperature superconductivity. With the Eliashberg theory and with the electronic structure determined by ARPES and the electronic dielectric function obtained by the softened dispersion of the in-pane Cu–O stretching mode, we calculated the transition temperature and the order parameter at the transition temperature. The order parameter is of the d(x2-y2) symmetry and the transition temperature is well in excess of 100 K.

scholarly journals EFFECTS OF c-AXIS HOPPING IN THE INTERLAYER TUNNELING MODEL OF HIGH-Tc LAYERED CUPRATES

1999 ◽  
Vol 13 (13) ◽  
pp. 1619-1632
Author(s):  
BIPLAB CHATTOPADHYAY ◽  
A. N. DAS
Keyword(s):  
Experimental Data ◽  
Transition Temperature ◽  
Cuprate Superconductors ◽  
Interlayer Coupling ◽  
Superconducting Gap ◽  
Tunneling Model ◽  
High Tc ◽  
Optimal Doping ◽  
Pair Tunneling ◽  
Layered Cuprates

We consider the interlayer pair-tunneling model for layered cuprates, including an effective single particle hopping along the c-axis. A phenomenological suppression of the c-axis hopping matrix element, by the pseudogap in cuprate superconductors, is incorporated. At optimal doping, quantities characteristic to the superconducting state, such as the transition temperature and the superconducting gap are calculated. Results from our calculations are consistent with the experimental observations with the noteworthy point that, the superconducting gap as a function of temperature shows excellent match to the experimental data. Predictions within the model, regarding T c variation with interlayer coupling, are natural outcomes which could be tested further.

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].

scholarly journals Unusual symmetries of the order parameter in cuprates

2020 ◽  
Vol 2 (4) ◽  
pp. 207-212
Author(s):  
Tran Van Luong ◽  
Nguyen Thi Ngoc Nu
Keyword(s):  
High Temperature ◽  
Order Parameter ◽  
Cuprate Superconductors ◽  
High Temperature Superconductivity ◽  
Spin Fluctuation ◽  
High Temperature Superconductors ◽  
Coulomb Repulsion ◽  
Bcs Theory ◽  
S Wave ◽  
Wave Symmetry

The BCS superconducting theory, introduced by J. Bardeen, L. Cooper and R. Schriffer in 1957, succeeded in describing and satis-factorily explaining the nature of superconductivity for low-temperature superconductors. However, the BCS theory cannot explain the properties of high-temperature superconductors, discovered by J. G. Bednorz and K. A. Müller in 1986. Although scientists have found a lot of new superconductors and their transition temperatures are constantly increasing, most high-temperature superconductors are found by experiment and so far no theory can fully explain their properties. Many previous studies have suggested that the order parameter in high-temperature copper-based superconductors (cuprate superconductors - cuprates) is in the form of d-wave symmetry, but recent results show that the order parameter has an extended s-wave symmetry (extended s wave). Studying the symmetric forms of order parameters in cuprate can contribute to understanding the nature of high-temperature superconductivity. In this article, the authors present an overview of the development of high-temperature supercon-ductors over the past 30 years and explains unusual symmetries of the order parameter in copper-based superconductors. The com-petition of three coupling mechanisms of electrons in cuprates (the mechanism of coupling through coulomb repulsion, electron-phonon mechanism and spin-fluctuation mechanism) affects the unusual symmetry of the order parameter. The solution of the self-consistency equation in simple cases has been found and the ability to move the phase within the superconducting state has been shown.

CRITICAL TEMPERATURE OF HIGH-Tc SUPERCONDUCTORS AND BOUNDARY CONDITIONS IN GINZBURG-LANDAU THEORY

2009 ◽  
Vol 23 (20n21) ◽  
pp. 4269-4276 ◽  
Author(s):  
A. LYKOV
Keyword(s):  
Boundary Condition ◽  
Critical Temperature ◽  
Order Parameter ◽  
Cuprate Superconductors ◽  
Landau Theory ◽  
Structural Elements ◽  
High Tc Superconductors ◽  
Ginzburg Landau ◽  
High Tc ◽  
Insulating Properties

New boundary condition for the order parameter in the Ginzburg-Landau theory is applied to the case of CuO 2 planes which are the main structural elements responsible for superconductivity in high-Tc superconductors. It was found that the order parameter in these superconductors is significantly depressed in the CuO 2 planes. As a result, this boundary condition to the GL equations is found to limit the critical temperature of high-Tc superconductors. Thus, in order to increase Tc of cuprate superconductors, the number of CuO 2 planes that are within a short distance of each other in unit cell or insulating properties of the layers located in the vicinity to the CuO 2 planes should be increased.

scholarly journals Review on origin of the unusual high-Tc superconductivity in Ca1−xRExFe2As2 (RE = La, Ce, Pr, Nd)

2015 ◽  
Vol 1 (1) ◽  
Author(s):  
W. Zhou ◽  
Z. X. Shi
Keyword(s):  
High Temperature ◽  
Transition Temperature ◽  
Crystal Structures ◽  
High Temperature Superconductivity ◽  
Iron Pnictides ◽  
Iron Based Superconductors ◽  
High Tc ◽  
High Tc Superconductivity ◽  
Iron Based

AbstractSince the discovery of high temperature superconductivity in iron pnictides in 2008, many iron-based superconductors (IBSs) with various crystal structures have been exploited.Among them, superconductivity with the onset transition temperature T

scholarly journals A Review on Cuprate Based Superconducting Materials

2019 ◽  
Vol 3 (1) ◽  
Keyword(s):  
Transition Temperature ◽  
Copper Oxide ◽  
Cuprate Superconductors ◽  
High Temperature Superconductivity ◽  
Ambient Pressure ◽  
Applied Pressure ◽  
Barium Copper Oxide ◽  
Normal Pressure ◽  
Liquid Nitrogen Temperature ◽  
Barium Copper

When Bednorz and Müller discovered the superconductivity in a compound La-Ba-Cu-O in 1986, it was considered as a breakthrough in the research of the superconductivity. This leads to the discovery of the other cuprate superconductors, and immediately the transition temperature of the synthesized materials reached to the liquid nitrogen temperature. Today the maximum transition temperature of the cuprate superconductors changes from 35 K for La2 −xSrx CuO4 to 138 K for Hg1−xTlx Ba2 Ca2 Cu3 Oy (the highest record under normal pressure, which extends to ∼160K at high pressure). High-temperature superconductivity in the Non-stoichiometric cuprate lanthanum barium copper oxide . The Tc for this material was 35 K, well above the previous record of 23K. Thousands of publications examine the superconductivity in cuprates between 1986 and 2001, and Bednorz and Müller were awarded the Nobel Prize in Physics only a year after their discovery. From 1986 to 2008, many cuprate superconductors were identified, the most famous being yttrium barium copper oxide (YBa2 Cu3 O7 , "YBCO" or "1-2-3"). Another example is bismuth strontium calcium copper oxide (BSCCO or Bi2 Sr2 Can Cun+1O2n+6-d ) with Tc = 95–107 K depending on the n value. Thallium barium calcium copper oxide (TBCCO, TlmBa2 Can−1Cun O2n+m+2+δ ) was the next class of high-Tc cuprate superconductors with Tc = 127 K observed in Tl2 Ba2 Ca2 Cu3 O10 (TBCCO-2223) in 1988. The highest confirmed, ambient-pressure, Tc is 135 K, achieved in 1993 with the layered cuprate HgBa2 Ca2 Cu3 O8+x. few months later, another team measured superconductivity above 150K in the same compound under applied pressure (153 K at 150 k bar).

COMMON MAGNETIC ORIGIN OF THE RESONANCE PEAK AND INCOMMENSURATION IN HIGH-Tc SUPERCONDUCTORS

2000 ◽  
Vol 14 (29n31) ◽  
pp. 3334-3341 ◽  
Author(s):  
C. D. BATISTA ◽  
G. ORTIZ ◽  
A. V. BALATSKY
Keyword(s):  
Transition Temperature ◽  
Superconducting Transition Temperature ◽  
Cuprate Superconductors ◽  
Resonance Peak ◽  
Low Energy ◽  
Unified Theory ◽  
Superconducting Transition ◽  
High Tc Superconductors ◽  
High Tc ◽  
Magnetic Origin

We present a unified theory for the resonance peak and low-energy incommensurate response observed in high-Tc cuprate superconductors. The origin of both features is purely magnetic and they represent universal features signaling the existence of an incommensurate spin state both below and above the superconducting transition temperature. We argue that the resonance peak is the reflection of commensurate antiferromagnetism. Our theoretical scenario gives an account of the main universal features observed in various families of superconductors and predicts those that have not been observed yet experimentally.

THE EVOLUTION OF HIGH-TEMPERATURE SUPERCONDUCTIVITY: THEORY PERSPECTIVE

2010 ◽  
Vol 24 (20n21) ◽  
pp. 4150-4180 ◽  
Author(s):  
Elihu Abrahams
Keyword(s):  
High Temperature ◽  
Transition Temperature ◽  
Cuprate Superconductors ◽  
High Temperature Superconductivity ◽  
High Transition Temperature ◽  
High Transition ◽  
Superconductivity Theory ◽  
Theoretical Developments

Theoretical developments concerning the high transition temperature cuprate superconductors are reviewed.

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