Diatomic molecules and 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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Halogens molecular modifications with high pressure: the case of iodine

Physical Chemistry Chemical Physics ◽

10.1039/d0cp05942k ◽

2021 ◽

Author(s):

Jingming Shi ◽

Emiliano Fonda ◽

Silvana Botti ◽

Miguel A. L. Marques ◽

Toru Shinmei ◽

...

Keyword(s):

High Pressure ◽

Absorption Spectroscopy ◽

Diatomic Molecules ◽

Giant Planets ◽

Atomistic Modeling ◽

X Ray ◽

X Ray Absorption

Metallization and dissociation are key transformations in diatomic molecules at high densities particularly significant for modeling giant planets. Using X-ray absorption spectroscopy and atomistic modeling, we demonstrate that in halogens,...

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