Noisy Cooper pairs

The Bose–Einstein condensation and appearance of superfluidity and superconductivity are introduced from basic phenomena. A systematic theory based on the asymmetric expansion of chapter 11 is shown to correct the T-matrix from unphysical multiple-scattering events. The resulting generalised Soven scheme provides the Beliaev equations for Boson’s and the Nambu–Gorkov equations for fermions without the usage of anomalous and non-conserving propagators. This systematic theory allows calculating the fluctuations above and below the critical parameters. Gap equations and Bogoliubov–DeGennes equations are derived from this theory. Interacting Bose systems with finite temperatures are discussed with successively better approximations ranging from Bogoliubov and Popov up to corrected T-matrices. For superconductivity, the asymmetric theory leading to the corrected T-matrix allows for establishing the stability of the condensate and decides correctly about the pair-breaking mechanisms in contrast to conventional approaches. The relation between the correlated density from nonlocal kinetic theory and the density of Cooper pairs is shown.

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Multiplicity, Parity and Angular Momentum of a Cooper Pair in Unconventional Superconductors of D4h Symmetry: Sr2RuO4 and Fe-Pnictide Materials

Symmetry ◽

10.3390/sym13081435 ◽

2021 ◽

Vol 13 (8) ◽

pp. 1435

Author(s):

Victor G. Yarzhemsky

Keyword(s):

Angular Momentum ◽

Cooper Pair ◽

Point Group ◽

Group Symmetry ◽

Cooper Pairs ◽

Group Approach ◽

Angular Momentum Projection ◽

Space Group ◽

Unconventional Superconductors ◽

Even Pairs

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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On-demand thermoelectric generation of equal-spin Cooper pairs

Physical Review Research ◽

10.1103/physrevresearch.2.022019 ◽

2020 ◽

Vol 2 (2) ◽

Cited By ~ 3

Author(s):

Felix Keidel ◽

Sun-Yong Hwang ◽

Björn Trauzettel ◽

Björn Sothmann ◽

Pablo Burset

Keyword(s):

Cooper Pairs ◽

Thermoelectric Generation ◽

On Demand

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Incoherent tunneling of the cooper pairs and magnetic flux quanta in ultrasmall Josephson junctions

Physica B Condensed Matter ◽

10.1016/s0921-4526(09)80058-6 ◽

1990 ◽

Vol 165-166 ◽

pp. 945-946 ◽

Cited By ~ 90

Author(s):

D.V. Averin ◽

Yu.V. Nazarov ◽

A.A. Odintsov

Keyword(s):

Magnetic Flux ◽

Josephson Junctions ◽

Cooper Pairs

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Quantum nanoelectromechanics with electrons, quasi-particles and Cooper pairs: effective bath descriptions and strong feedback effects

New Journal of Physics ◽

10.1088/1367-2630/7/1/238 ◽

2005 ◽

Vol 7 ◽

pp. 238-238 ◽

Cited By ~ 83

Author(s):

Aashish A Clerk ◽

Steven Bennett

Keyword(s):

Cooper Pairs ◽

Feedback Effects

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Superconducting coherence length of hole-doped cuprates obtained from electron–boson spectral density function

Scientific Reports ◽

10.1038/s41598-021-91163-w ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Jungseek Hwang

Keyword(s):

Spectral Density ◽

Coherence Length ◽

Cooper Pair ◽

Average Frequency ◽

Spin Fluctuations ◽

Fermi Velocity ◽

Cooper Pairs ◽

Spectroscopic Techniques ◽

Microscopic Mechanism ◽

Superconducting Coherence Length

AbstractElectron–boson spectral density functions (EBSDFs) can be obtained from measured spectra using various spectroscopic techniques, including optical spectroscopy. EBSDFs, known as glue functions, are suggested to have a magnetic origin. Here, we investigated EBSDFs obtained from the measured optical spectra of hole-doped cuprates with wide doping levels, from underdoped to overdoped cuprates. The average frequency of an EBSDF provides the timescale for the spin fluctuations to form Cooper pairs. This timescale is directly associated with retarded interactions between electrons. Using this timescale and Fermi velocity, a reasonable superconducting coherence length, which reflects the size of the Cooper pair, can be extracted. The obtained coherence lengths were consistent with those measured via other experimental techniques. Therefore, the formation of Cooper pairs in cuprates can be explained by spin fluctuations, the timescales of which appear in EBSDFs. Consequently, EBSDFs provide crucial information on the timescale of the microscopic mechanism of Cooper pair formation.

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Electric-Field Induced Formation of Superconducting Granular Balls

International Journal of Modern Physics B ◽

10.1142/s021797920201261x ◽

2002 ◽

Vol 16 (17n18) ◽

pp. 2529-2535

Author(s):

R. Tao ◽

X. Xu ◽

Y. C. Lan

Keyword(s):

Surface Energy ◽

Electric Field ◽

Liquid Nitrogen ◽

Applied Electric Field ◽

Strong Electric Field ◽

Particle Surface ◽

Cooper Pairs ◽

Surface Charges

When a strong electric field is applied to a suspension of micron-sized high T c superconducting particles in liquid nitrogen, the particles quickly aggregate together to form millimeter-size balls. The balls are sturdy, surviving constant heavy collisions with the electrodes, while they hold over 106 particles each. The phenomenon is a result of interaction between Cooper pairs and the strong electric field. The strong electric field induces surface charges on the particle surface. When the applied electric field is strong enough, Cooper pairs near the surface are depleted, leading to a positive surface energy. The minimization of this surface energy leads to the aggregation of particles to form balls.

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