Bogoliubov Fermi Surfaces in Superconductors with Broken Time-Reversal Symmetry

Agterberg, D. F.; Brydon, P. M. R.; Timm, Carsten

doi:10.1103/physrevlett.118.127001

Cited by 221 publications

(333 citation statements)

References 41 publications

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“…While the former class includes topological insulators and superconductors, but also quantum Hall states [5][6][7], the latter class concerns topological semimetals (e.g. Weyl, Dirac and nodal-line semimetals), which have been intensively investigated in the recent years [8][9][10][11][12][13][14][15][16][17][18]; besides, topological phases with nodal surfaces have also been theoretically proposed [19][20][21][22][23]. These gapless systems can display remarkable properties, such as Fermi arcs or drumhead surface states on the boundaries, and momentum-space Dirac monopoles in the bulk.…”

mentioning

confidence: 99%

Floquet-engineering of nodal rings and nodal spheres and their characterization using the quantum metric

Salerno

Goldman

Palumbo

2020

Phys. Rev. Research

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Semimetals exhibiting nodal lines or nodal surfaces represent a novel class of topological states of matter. While conventional Weyl semimetals exhibit momentum-space Dirac monopoles, these more exotic semimetals can feature unusual topological defects that are analogous to extended monopoles. In this work, we describe a scheme by which nodal rings and nodal spheres can be realized in synthetic quantum matter through well-defined periodic-driving protocols. As a central result of our work, we characterize these nodal defects through the quantum metric, which is a gauge-invariant quantity associated with the geometry of quantum states. In the case of nodal rings, where the Berry curvature and conventional topological responses are absent, we show that the quantum metric provides an observable signature for these extended topological defects. Besides, we demonstrate that quantum-metric measurements could be exploited to directly detect the topological charge associated with a nodal sphere. We discuss possible experimental implementations of Floquet nodal defects in few-level atomic systems, paving the way for the exploration of Floquet extended monopoles in quantum matter. arXiv:1912.00930v1 [cond-mat.mes-hall]

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confidence: 99%

Floquet-engineering of nodal rings and nodal spheres and their characterization using the quantum metric

Salerno

Goldman

Palumbo

2020

Phys. Rev. Research

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“…Gap structures of the latter kind have recently been introduced in Ref. [30], where it was shown that these nodal degeneracies of codimension-1 are topologically stable in parity-even multiband superconductors with spontaneously broken time-reversal symmetry.…”

Section: Quasiparticle Gap Structures and Topologymentioning

confidence: 99%

“…This ignores the effects of coupling to the conduction band captured by Eq. (45) and potentially misses qualitative features of the gap structure with topological origin [30]. Let us therefore take a more formal approach which can account for all constraints imposed by the symmetry of the system.…”

Section: Quasiparticle Gap Structures and Topologymentioning

confidence: 99%

Pairing States of Spin- 32 Fermions: Symmetry-Enforced Topological Gap Functions

Venderbos¹,

Savary²,

Ruhman³

et al. 2018

Phys. Rev. X

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We study the topological properties of superconductors with paired j ¼ 3 2 quasiparticles. Higher spin Fermi surfaces can arise, for instance, in strongly spin-orbit coupled band-inverted semimetals. Examples include the Bi-based half-Heusler materials, which have recently been established as low-temperature and low-carrier density superconductors. Motivated by this experimental observation, we obtain a comprehensive symmetry-based classification of topological pairing states in systems with higher angular momentum Cooper pairing. Our study consists of two main parts. First, we develop the phenomenological theory of multicomponent (i.e., higher angular momentum) pairing by classifying the stationary points of the free energy within a Ginzburg-Landau framework. Based on the symmetry classification of stationary pairing states, we then derive the symmetry-imposed constraints on their gap structures. We find that, depending on the symmetry quantum numbers of the Cooper pairs, different types of topological pairing states can occur: fully gapped topological superconductors in class DIII, Dirac superconductors, and superconductors hosting Majorana fermions. Notably, we find a series of nematic fully gapped topological superconductors, as well as double-and triple-Dirac superconductors, with quadratic and cubic dispersion, respectively. Our approach, applied here to the case of j ¼ 3 2 Cooper pairing, is rooted in the symmetry properties of pairing states, and can therefore also be applied to other systems with higher angular momentum and high-spin pairing. We conclude by relating our results to experimentally accessible signatures in thermodynamic and dynamic probes.

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“…The Cooper pair wave function is symmetric in the crystal momentum and spin channels but it is anti-symmetric with respect to the orbital degree of freedom. Recent studies [11,[30][31][32][33][34][35][36][37][38] in several materials, including the Iron based superconductors, half-Heusler compounds, UPt 3 and Sr 2 RuO 4 , have also pointed out the importance of internal degrees of freedom of electrons (coming from, for example, sublattice or multiple orbitals) in determining the pairing symmetries of superconducting ground states.…”

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confidence: 99%

Quantitative theory of triplet pairing in the unconventional superconductor LaNiGa2

et al. 2020

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The exceptionally low-symmetry crystal structures of the time-reversal symmetry breaking superconductors LaNiC2 and LaNiGa2 lead to an internally-antisymmetric non-unitary triplet (INT) state as the only possibility compatible with experiments. We argue that this state has a distinct signature: a double-peak structure in the Density of States (DOS) which resolves in the spin channel in a particular way. We construct a detailed model of LaNiGa2 capturing its electronic band structure and magnetic properties ab initio. The pairing mechanism is described via a single adjustable parameter. The latter is fixed by the critical temperature Tc allowing parameter-free predictions. We compute the electronic specific heat and find excellent agreement with experiment. The size of the ordered moment in the superconducting state is compatible with zero-field muon spin relaxation experiments and the predicted spin-resolved DOS suggests the spin-splitting is within the reach of present experimental technology. arXiv:1912.08160v2 [cond-mat.supr-con]

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Bogoliubov Fermi Surfaces in Superconductors with Broken Time-Reversal Symmetry

Cited by 221 publications

References 41 publications

Floquet-engineering of nodal rings and nodal spheres and their characterization using the quantum metric

Floquet-engineering of nodal rings and nodal spheres and their characterization using the quantum metric

Pairing States of Spin- 32 Fermions: Symmetry-Enforced Topological Gap Functions

Quantitative theory of triplet pairing in the unconventional superconductor LaNiGa2

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