Single branch of chiral Majorana modes from doubly degenerate Fermi surfaces

Wang, Yang; Xu, Chao; Wu, Congjun

doi:10.1103/physrevresearch.2.042047

Cited by 16 publications

(12 citation statements)

References 64 publications

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“…In the following, we assume that each band is weakly coupled and the intraband pairing is dominant compared to the interband pairing. In such situations, spontaneous T -symmetry breaking with maintaining the PT -symmetry is energetically favored in the mixed-parity superconducting states 15,16 , and the symmetry of the superconducting order parameter becomes equivalent to that of odd-parity magnetic multipoles 44 . A characteristic feature of the odd-parity magnetic multipole ordered state is the asymmetric modulation of the band structure 51,52,59,60 , which leads to peculiar nonequilibrium responses such as nonreciprocal transport 61 , magnetopiezoelectric effect 62,63 , and photocurrent generation 48,49 .…”

Section: Resultsmentioning

confidence: 99%

“…The P-symmetry is broken in such superconductors. Furthermore, spontaneous T -symmetry breaking realized by the ±π/2 phase difference between even-and odd-parity pairing potentials is energetically favored [15][16][17] (Fig. 1a), when the spin-orbit coupling (SOC) due to noncentrosymmetric crystal structure is absent or weak.…”

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confidence: 99%

“…In previous works, the mixed-parity superconductivity has been theoretically studied mainly in single-band models for spin-1/2 fermions 15,16,[18][19][20][21]23 . On the other hand, it has recently been recognized that the multiband structure of the Cooper pair's wave function arising from internal electronic degrees of freedom (DOF) (e.g., orbital and sublattice) induces exotic superconducting phenomena.…”

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confidence: 99%

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Anapole superconductivity from $${{{{{{{\mathcal{PT}}}}}}}}$$-symmetric mixed-parity interband pairing

Kanasugi

Yanase

2022

Commun Phys

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Recently, superconductivity with spontaneous time-reversal or parity symmetry breaking is attracting much attention owing to its exotic properties, such as nontrivial topology and nonreciprocal transport. Particularly fascinating phenomena are expected when the time-reversal and parity symmetry are simultaneously broken. This work shows that time-reversal symmetry-breaking mixed-parity superconducting states generally exhibit an unusual asymmetric Bogoliubov spectrum due to nonunitary interband pairing. For generic two-band models, we derive the necessary conditions for the asymmetric Bogoliubov spectrum. We also demonstrate that the asymmetric Bogoliubov quasiparticles lead to the effective anapole moment of the superconducting state, which stabilizes a nonuniform Fulde-Ferrell-Larkin-Ovchinnikov state at zero magnetic fields. The concept of anapole order employed in nuclear physics, magnetic materials science, strongly correlated electron systems, and optoelectronics is extended to superconductors by this work. Our conclusions are relevant for any multiband superconductors with competing even- and odd-parity pairing channels. Especially, we discuss the superconductivity in UTe2.

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Anapole superconductivity from $${{{{{{{\mathcal{PT}}}}}}}}$$-symmetric mixed-parity interband pairing

Kanasugi

Yanase

2022

Commun Phys

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“…In particular, taking the atomic orbital degrees of freedom into account, the classification of unconventional pairing states could be significantly enriched. Among them, SCs with spontaneous time-reversal symmetry (TRS) breaking are of special interest, in which two mutually exclusive quantum phenomena, magnetism and superconductivity, may coexist [38][39][40][41][42][43].…”

Section: Introductionmentioning

confidence: 99%

Spin-orbit-coupled superconductivity with spin-singlet non-unitary pairing

Zeng¹,

Xu²,

Wang³

et al. 2022

Preprint

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An unconventional superconductor is distinguished with two types of gap functions: unitary and non-unitary. This core subject has been concentrated on purely spin-triplet or singlet-triplet mixed superconductors. However, the generalization to a purely spin-singlet superconductor has remained primarily of theoretical interest, which requires at least a multi-orbital correlated electronic systems. In this work, we present a possible establishment of both unitary and non-unitary pairings for spin-singlet superconductors with two atomic orbitals. Then we investigate the effects of atomic spin-orbit coupling and find a new spin-orbit-coupled non-unitary superconductor that supports exotic phenomena. Remarkably, there are mainly three features. Firstly, the atomic spin-orbit coupling locks the electron spins to be out-of-plane, which could give birth to the Type II Ising superconductivity with a large in-plane upper critical field compared to the Pauli limit. Secondly, topological chiral or helical Majorana edge state could be realized even in the absence of external magnetic fields or Zeeman fields. In addition, a spin-polarized superconducting state could even be generated by spin-singlet non-unitary pairings with spontaneous time-reversal breaking, which severs as a smoking gun to detect this exotic state by measuring the spin-resolved density of states. Therefore, our work might pave a new avenue to spin-orbit-coupled superconductors with spin-singlet non-unitary pairing symmetries.

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“…{d xz , d yz }-orbitals) into account, the classification of unconventional pairing states is significantly enriched. Among them, SCs with spontaneous timereversal-symmetry (TRS) breaking pairing symmetries are of special interest [31][32][33][34][35][36]. Besides, the unconventional orbital-dependent pairing states are intriguing to be explored, for example, c dxz,↑ (k)c dyz,↓ (−k)−[↑↔↓] and c dxz,↑ (k)c dxz,↓ (−k) − c dyz,↑ (k)c dyz,↓ (−k) − [↑↔↓], however, they have been less studied.…”

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confidence: 99%

Pseudospin-Triplet Pairing in Iron-Chalcogenide Superconductors and Magic-Angle Twisted Bilayer Graphene

Zeng¹,

Xu²,

Wang³

et al. 2021

Preprint

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In this work, we study even-parity spin-singlet orbital-triplet pairing states for a two-band superconductor. An orbital do(k)-vector is introduced to characterize orbital-dependent pairings, in analogy to the spin ds(k)-vector that describes spin-triplet pairings in 3 He superfluid. Naively, one might think the double degeneracy of orbitals would be lifted by inter-orbital hybridizations due to crystal fields or electron-electron repulsive interactions, then spin-singlet orbital-dependent pairings may be severely suppressed. However, we demonstrate that orbital-triplet pairing, represented by the orbital do(k)-vector, could exist under some circumstances. Remarkably, it could even coexist with nematic orders or charge-density-wave orders induced by interactions. The generalization to a single-band superconductor with two valleys (e.g. honeycomb lattice with two sublattices) is also discussed. Moreover, the complex orbital do-vector spontaneously breaks time-reversal symmetry (TRS), which might give rise to the TRS-breaking orbital-polarization, analogous to the spin magnetism.

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Single branch of chiral Majorana modes from doubly degenerate Fermi surfaces

Cited by 16 publications

References 64 publications

Anapole superconductivity from $${{{{{{{\mathcal{PT}}}}}}}}$$-symmetric mixed-parity interband pairing

Anapole superconductivity from $${{{{{{{\mathcal{PT}}}}}}}}$$-symmetric mixed-parity interband pairing

Spin-orbit-coupled superconductivity with spin-singlet non-unitary pairing

Pseudospin-Triplet Pairing in Iron-Chalcogenide Superconductors and Magic-Angle Twisted Bilayer Graphene

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