scholarly journals TO PROBE THE PHASE OF THE ORDER PARAMETER IN HIGH-TEMPERATURE SUPERCONDUCTORS BY USING r.f. SQUID

1999 ◽  
Vol 48 (12) ◽  
pp. 2364
Author(s):  
DU SHENG-WANG ◽  
DAI YUAN-DONG ◽  
WANG SHI-GUANG
Keyword(s):  
High Temperature ◽  
Order Parameter ◽  
High Temperature Superconductors

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.

Effect of hybridization parity on multiband superconductors properties

2021 ◽  
pp. 2150102
Author(s):  
W. M. P. Ramos ◽  
I. T. Padilha
Keyword(s):  
High Temperature ◽  
Phase Diagrams ◽  
Finite Temperature ◽  
Order Parameter ◽  
Heavy Fermions ◽  
High Temperature Superconductors ◽  
Unconventional Superconductors ◽  
First Case ◽  
The One ◽  
Multiband Superconductors

We investigated the influence that hybridization parity has on the so-called multiband superconductors, where we proposed a model with two bands [Formula: see text] and [Formula: see text]. Thus, we observe the behavior of intra-band superconductivity, the one whose coupling occurs between carriers that belong to the same band [Formula: see text] or [Formula: see text], and inter-bands, when the coupling occurs between carriers of different bands [Formula: see text] with [Formula: see text] — from graphs of the order parameter as a function of hybridization and the order parameter as a function of temperature, for null temperature in the first case and for finite temperature in the second, as well as intraband phase diagrams. In this sense, the study of the influence that hybridization has on superconductivity is fundamental for understanding unconventional superconductors, such as heavy fermions and high-temperature superconductors.

scholarly journals Order-parameter symmetries in high-temperature superconductors

2000 ◽  
Vol 61 (9) ◽  
pp. 5913-5916 ◽  
Author(s):  
R. A. Klemm ◽  
C. T. Rieck ◽  
K. Scharnberg
Keyword(s):  
High Temperature ◽  
Order Parameter ◽  
High Temperature Superconductors

What is the Symmetry of the High-Tc Order Parameter?

1998 ◽  
Vol 12 (29n31) ◽  
pp. 2920-2931 ◽  
Author(s):  
Richard A. Klemm
Keyword(s):  
High Temperature ◽  
Order Parameter ◽  
High Temperature Superconductors ◽  
Density Wave ◽  
Spin Density Wave ◽  
Superconducting Gap ◽  
S Wave ◽  
Orbital Symmetry ◽  
High Tc ◽  
Phase Sensitive

In recent years, there has been a raging controversy regarding the orbital symmetry of the superconducting order parameter (OP) in the high temperature superconductors. Many experiments were interpreted in terms of a dx2-y2-wave OP, but many others were interpreted in terms of a more conventional s-wave OP. We review the problems of both intrinsic and extrinsic natures with the phase-sensitive experiments on YBCO. We further show that the photoemission experiments of the purported superconducting gap in Bi2Sr2CaCu2O 8+δ are entirely consistent with charge- and/or spin-density wave formation in that material. The presence of such density waves greatly complicates the analysis of most experiments. Hence, we conclude that the orbital symmetry of the superconducting OP is still unknown in any of the high temperature superconductors.

COOPER–PAIR SUPERFLUID STATE IN HIGH-TEMPERATURE SUPERCONDUCTORS

2000 ◽  
Vol 14 (11) ◽  
pp. 1225-1237
Author(s):  
ZENG-BING CHEN
Keyword(s):  
High Temperature ◽  
Order Parameter ◽  
High Temperature Superconductors ◽  
Quantum Fluctuations ◽  
Superconducting Order Parameter ◽  
Cooper Pairs ◽  
Effective Hamiltonian ◽  
Superfluid State ◽  
Bosonic Field ◽  
Granular Superconductors

We propose a lattice model of high-temperature superconductors based on their intrinsic granular-like structure. Due to the shortness of the coherent length in high-temperature superconductors, the superconducting order parameter can be well defined locally only in small regions, in which the number and the phase of the Cooper–pairs will experience strong quantum fluctuations. The "superconducting order parameter" in terms of the local number and phase operators of the Cooper–pairs is then regarded as an effective quantized bosonic field described by a discretized Ginzberg–Landau-type effective Hamiltonian, first proposed for granular superconductors and recently for high-temperature superconductors. The effective Hamiltonian also describes the quantum fluctuations of the superconducting order parameter. The global superconducting order sets in when the Cooper–pairs are in the superfluid state. This is in contrast to the previous picture, in which the phase coherence drives the system into the superconducting state when only the phase fluctuations of the superconducting order parameter are considered.

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