Topology of the superconducting order under pairing repulsion

Belyavsky, V. I.; Kopaev, Yu. V.; Nguyen, Nghia Q.; Tran, Vi-Do

doi:10.1134/s1063776109020137

Cited by 4 publications

(2 citation statements)

References 13 publications

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“…Nhiệm vụ đặt ra cho các nhà khoa học là tìm ra cơ chế siêu dẫn nhiệt độ cao để có cơ sở tìm kiếm các chất siêu dẫn có cấu trúc ổn định và nhiệt độ chuyển pha cao hơn. Cho tới nay, đã có rất nhiều giả thuyết khác nhau về cơ chế siêu dẫn nhiệt độ cao được đề cập, như : cơ chế electron-phonon7,8 , cơ chế ghép đôi thông qua lực đẩy Coulomb[9][10][11][12] , cơ chế thăng giáng spin (trao đổi magnon)13,14 ,… tuy nhiên chưa có giả thuyết nào có thể giải thích được tất cả các hiện tượng thực nghiệm mở rộng (extended s wave)16,17 . Một số tác giả còn chứng tỏ rằng có sự thay đổi tính chất đối xứng của tham số trật tự tùy thuộc vào nồng độ pha tạp18,19 .…”

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Unusual symmetries of the order parameter in cuprates

Luong

2020

Sci. Tech. Dev. J.- Eng. Tech.

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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.

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Unusual symmetries of the order parameter in cuprates

Luong

2020

Sci. Tech. Dev. J.- Eng. Tech.

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“…Coefficients in such linear combinations specifies the orbital symmetry of the order parameter. 23 Coefficients of like signs correspond to extended swave symmetry (the order parameter is invariant with respect to rotation by π/2 about C 4 axis). In the case of coefficients of unlike signs, the order parameter reverses sign under rotation by π/2 and therefore can be referred to d-wave orbital symmetry.…”

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Chiral d-wave superconductor with nonzero center-of-mass pair momentum

Belyavsky¹,

Kapaev²,

Kopaev³

2012

Preprint

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Hypothetical topologically nontrivial superconducting state of two-dimensional electron system is discussed in connection with the problem of pairing with large center-of-mass pair momentum under predominant repulsive screened Coulomb interaction. Direct numerical solution of the selfconsistency equation exhibits two nearly degenerate order parameters which can be formally referred to dx 2 −y 2 and d xy orbital symmetry. Spontaneous breaking of the time-reversal symmetry can mix these states and form fully gapped chiral d + id superconducting state.

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