On electron pairing in unconventional superconductors

Sr2RuO4 and Fe-pnictide superconductors belong to the same point group symmetry D4h. Many experimental data confirm odd pairs in Sr2RuO4 and even pairs in Fe-pnictides, but opposite conclusions also exist. Recent NMR results of Pustogow et al., which revealed even Cooper pairs in Sr2RuO4, require reconsideration of symmetry treatment of its SOP (superconducting order parameter). In the present work making use of the Mackey–Bradley theorem on symmetrized squares, a group theoretical investigation of possible pairing states in D4h symmetry is performed. It is obtained for I4/mmm , i.e., space group of Sr2RuO4, that triplet pairs with even spatial parts are possible in kz direction and in points M and Y. For the two latter cases pairing of equivalent electrons with nonzero total momentum is proposed. In P4/nmm space group of Fe- pnictides in point M, even and odd pairs are possible for singlet and triplet cases. It it shown that even and odd chiral states with angular momentum projection m=±1 have nodes in vertical planes, but Eg is nodal , whereas Eu is nodeless in the basal plane. It is also shown that the widely accepted assertion that the parity of angular momentum value is directly connected with the spatial parity of a pair is not valid in a space-group approach to the wavefunction of a Cooper pair.

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The Superconducting Critical Temperature

Symmetry ◽

10.3390/sym13050911 ◽

2021 ◽

Vol 13 (5) ◽

pp. 911

Author(s):

Mike Guidry ◽

Yang Sun ◽

Lian-Ao Wu

Keyword(s):

Critical Temperature ◽

Dynamical Symmetry ◽

Many Body ◽

Unconventional Superconductors ◽

The Many ◽

Pair Coupling ◽

Intrinsic Strength ◽

Superconducting Transitions

Two principles govern the critical temperature for superconducting transitions: (1) intrinsic strength of the pair coupling and (2) the effect of the many-body environments on the efficiency of that coupling. Most discussions take into account only the former, but we argue that the properties of unconventional superconductors are governed more often by the latter, through dynamical symmetry relating to normal and superconducting states. Differentiating these effects is essential to charting a path to the highest-temperature superconductors.

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Evidence for Spin-Triplet Electron Pairing in the Proximity-Induced Superconducting State of an Fe-Doped InAs Semiconductor

Physical Review Letters ◽

10.1103/physrevlett.122.107001 ◽

2019 ◽

Vol 122 (10) ◽

Cited By ~ 3

Author(s):

Taketomo Nakamura ◽

Le Duc Anh ◽

Yoshiaki Hashimoto ◽

Shinobu Ohya ◽

Masaaki Tanaka ◽

...

Keyword(s):

Superconducting State ◽

Electron Pairing ◽

Spin Triplet

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Possibility of electron pairing in small metallic nanoparticles

Physical Review B ◽

10.1103/physrevb.84.064532 ◽

2011 ◽

Vol 84 (6) ◽

Cited By ~ 14

Author(s):

Ze’ev Lindenfeld ◽

Eli Eisenberg ◽

Ron Lifshitz

Keyword(s):

Metallic Nanoparticles ◽

Electron Pairing

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Tunnelling effects on surface bound states in unconventional superconductors

Reports on Progress in Physics ◽

10.1088/0034-4885/63/10/202 ◽

2000 ◽

Vol 63 (10) ◽

pp. 1641-1724 ◽

Cited By ~ 764

Author(s):

Satoshi Kashiwaya ◽

Yukio Tanaka

Keyword(s):

Bound States ◽

Unconventional Superconductors ◽

Tunnelling Effects

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63,65Cu NMR and NQR in YBa2Cu3O7-δ

MRS Proceedings ◽

10.1557/proc-99-379 ◽

1987 ◽

Vol 99 ◽

Author(s):

W. W. Warren ◽

R. E. Walstedt ◽

R. F. Bell ◽

G. F. Brennert ◽

R. J. Cava ◽

...

Keyword(s):

Superconducting State ◽

High Field ◽

Nuclear Relaxation ◽

Relaxation Rates ◽

Structural Units ◽

Nmr Spectrum ◽

Electron Pairing

ABSTRACTNMR and NQR results are reported for 63,65Cu in YBa2Cu3O7-δ. Analysis of the high-field NMR spectrum indicates substantial disorder in the copper-oxygen planes. Nuclear relaxation rates are significantly different for copper in the chains and planes both above and below Tc and yield sharply different electron pairing energies on these structural units in the superconducting state.

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