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Unconventional Superconductivity in Heavy Fermion and Ruthenate Materials
Published in David A. Cardwell, David C. Larbalestier, I. Braginski Aleksander, Handbook of Superconductivity, 2023
For magnetic field applied parallel to the c-axis, Hc2 is near 5 T [118], the high ratio of Hc2/Tc being typical of heavy fermion superconductors and reflecting a very short coherence length. Near Hc2, NMR and neutron scattering measurements find that incommensurate spin-density-wave order coexists with finite-momentum-Cooper-paired superconductivity [68, 176], providing further evidence for intimate coupling of superconducivity and magnetism in CeCoIn5. The properties of the superconducting state have been studied with many different probes, as summarized in reference [119], and the consensus is that CeCoIn5 is a spin-singlet superconductor with a line node, indicating a d-wave order parameter. Applying a novel scanning microscopy technique of “Bogoliubov quasiparticle interference,” the pattern of nodes on individual Fermi surfaces has been mapped [5], and found to be consistent with a dx2-y2 order parameter. Moreover, comparison with magnetic interactions, also extracted from quasiparticle interference, provides strong evidence that fluctuating f-electron magnetism is the pairing mechanism [167].
Effect of the nonmonotonic d-wave superconducting gap on the electronic Raman scattering of electron-doped cuprate superconductors
Published in Philosophical Magazine, 2020
Yuchen Zhang, Sheng Xu, Feng Yuan, Huaisong Zhao, Yong Zhou
In the SC state of cuprate superconductors, the Bogoliubov quasiparticle nature of the SC quasiparticle peak had been confirmed by ARPES experiments [46]. The SC state can be described by the Bardeen–Cooper–Schrieffer (BCS) formalism, in spite of the unconventional SC mechanism. The strong electron correlation effect may play a crucial role in explaining the main anomalous physical properties and the unconventional SC mechanism in cuprates. In this paper, we do not talk about the unconventional SC mechanism problems, but discuss the effect of a nonmonotonic d-wave symmetry SC gap on the electronic Raman scattering based on the phenomenological BCS Hamiltonian [45],where , and the parameters , [20,47], is the electron creation (annihilation) operator with spin σ, μ is the chemical potential, and the SC gap . The simple d-wave part , and the nonmonotonic d-wave part , and the coefficient B determines the strength of the next higher harmonics, indicates the nonmonotonic d-wave effect.
Emergence of a new symmetry class for Bogoliubov–de Gennes (BdG) Hamiltonians: expanding 10-fold symmetry classes
Published in Phase Transitions, 2020
In theoretical physics, different emergent particles appear as a Bogoliubov quasiparticles [16]. Here we state it very briefly. These Bogoliubov quasiparticles appear also as Majorana neutrinos of particle physics [17]. The other realization of Bogoliubov quasiparticles is in quantum many-body physics, quantum optics and specially in topological state of quantum many body systems [18]. The Bogoliubov quasiparticle appears in the solution of the Bogoliubov–de Gennes (BdG) Hamiltonian.