Superconducting pairing symmetry and spin-orbit coupling in proximitized graphene

2020 ◽  
Vol 102 (10) ◽  
Author(s):  
Abdulrhman M. Alsharari ◽  
Sergio E. Ulloa
Keyword(s):  
Pairing Symmetry ◽  
Orbit Coupling ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Superconducting Pairing

scholarly journals Theory of optical responses in clean multi-band superconductors

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Junyeong Ahn ◽  
Naoto Nagaosa
Keyword(s):  
Pairing Symmetry ◽  
Orbit Coupling ◽  
Optical Measurements ◽  
Inversion Symmetry ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Clean Limit ◽  
Optical Responses ◽  
Optical Excitations ◽  
Multi Band

AbstractElectromagnetic responses in superconductors provide valuable information on the pairing symmetry as well as physical quantities such as the superfluid density. However, at the superconducting gap energy scale, optical excitations of the Bogoliugov quasiparticles are forbidden in conventional Bardeen-Cooper-Schrieffer superconductors when momentum is conserved. Accordingly, far-infrared optical responses have been understood in the framework of a dirty-limit theory by Mattis and Bardeen for over 60 years. Here we show, by investigating the selection rules imposed by particle-hole symmetry and unitary symmetries, that intrinsic momentum-conserving optical excitations can occur in clean multi-band superconductors when one of the following three conditions is satisfied: (i) inversion symmetry breaking, (ii) symmetry protection of the Bogoliubov Fermi surfaces, or (iii) simply finite spin-orbit coupling with unbroken time reversal and inversion symmetries. This result indicates that clean-limit optical responses are common beyond the straightforward case of broken inversion symmetry. We apply our theory to optical responses in FeSe, a clean multi-band superconductor with inversion symmetry and significant spin-orbit coupling. This result paves the way for studying clean-limit superconductors through optical measurements.

Superconductivity in crystals with spin-orbit coupling

2020 ◽  
Vol 34 (33) ◽  
pp. 2030008
Author(s):  
K. V. Samokhin
Keyword(s):  
Point Group ◽  
Orbit Coupling ◽  
Gap Functions ◽  
Pure Spin ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Nodal Structure ◽  
General Symmetry ◽  
Interband Pairing ◽  
Superconducting Pairing

The electron Bloch states in crystals with spin-orbit coupling do not always transform under symmetry operations in the same way as the pure spin-1/2 states. This has profound consequences for the gap symmetry and nodal structure of superconductors. Based on the generalization of the Ueda–Rice prescription for the Bloch bases in twofold degenerate bands, we develop the general symmetry classification of multi-band superconducting pairing in non-magnetic centrosymmetric crystals. For the intraband pairing, we identify four exceptional cases in which the triplet gap function does not transform under the point group operations as a pseudovector, with a significant impact on the nodal structure. For the interband pairing, we show that the conventional ([Formula: see text]-wave) gap functions can have such unconventional features as triplet components and odd parity. The [Formula: see text]-wave interband pairing can also be odd in momentum and have a triplet component.

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