Photonic Weyl degeneracies in magnetized plasma

Gao, Wenlong; Yang, Biao; Lawrence, Mark; Fang, Fengzhou; Béri, Benjámin; Zhang, Shuang

doi:10.1038/ncomms12435

Cited by 169 publications

(168 citation statements)

References 44 publications

(62 reference statements)

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“…Meanwhile, for B x, the chiral modes still remain visible, clearly separated from the bulk states. We note in passing that the the boundary between type-I and type-II Weyl behaviour, realised at t 0x /t = 1.0 here, has been suggested as a stable phase in magnetic plasmas [40].…”

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confidence: 53%

Field-Selective Anomaly and Chiral Mode Reversal in Type-II Weyl Materials

2016

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Three-dimensional condensed matter incarnations of Weyl fermions generically have a tilted dispersion-in sharp contrast with their elusive high-energy relatives where a tilt is forbidden by Lorentz invariance, and with the low-energy excitations of two-dimensional graphene sheets where a tilt is forbidden by either crystalline or particle-hole symmetry. Very recently, a number of materials (MoTe2, LaAlGe and WTe2) have been identified as hosts of so-called type-II Weyl fermions whose dispersion is so strongly tilted that a Fermi surface is formed, whereby the Weyl node becomes a singular point connecting electron and hole pockets. We here predict that these systems have remarkable properties in presence of magnetic fields. Most saliently, we show that the nature of the chiral anomaly depends crucially on the relative angle between the applied field and the tilt, and that an inversion-asymmetric overtilting creates an imbalance in the number of chiral modes with positive and negative slopes. The field-selective anomaly gives a novel magneto-optical resonance, providing an experimental way to detect concealed Weyl nodes. [6,7], and have by now been confirmed to exist as quasi-particles in a rapidly growing list of materials displaying remarkable properties including topological Fermi arc surface states [4, 6-8] and a condensed matter incarnation of the chiral anomaly when exposed to external electromagnetic fields [9][10][11][12].The Weyl Hamiltonian pertinent to condensed matter,

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confidence: 53%

Field-Selective Anomaly and Chiral Mode Reversal in Type-II Weyl Materials

2016

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“…These crossing points in the momentum space are Weyl points with a finite Berry curvature and can in principle give non-trivial topological features (Gao et al, 2016a). Such a system is expected to have electromagnetic effects in reflection with no analog in electronic systems.…”

Section: E Possible Realizations In Non-electronic Systemsmentioning

confidence: 99%

Weyl and Dirac semimetals in three-dimensional solids

2018

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Weyl and Dirac semimetals are three dimensional phases of matter with gapless electronic excitations that are protected by topology and symmetry. As three dimensional analogs of graphene, they have generated much recent interest. Deep connections exist with particle physics models of relativistic chiral fermions, and -despite their gaplessness -to solid-state topological and Chern insulators. Their characteristic electronic properties lead to protected surface states and novel responses to applied electric and magnetic fields. The theoretical foundations of these phases, their proposed realizations in solid state systems, recent experiments on candidate materials, as well as their relation to other states of matter are reviewed.

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“…In addition to the standard Weyl points possessing a point-like Fermi surface (referred to as type-I), another type of Weyl point was more recently recognized, which has a conical Fermi surface (referred to as type-II) 13,[19][20][21] . Since the Weyl point or Weyl cone in Weyl semimetals represents a special dispersion of electrons moving in periodic potentials, the question naturally arises as to whether a similar dispersion or the Weyl point for classical waves propagating in artificial periodic structures exists [8][9][10][11][12][13][22][23][24][25][26][27][28] . Lu et al were the first to report the existence of Weyl points and the associated one-way SWs in photonic crystals based on double-gyroid structures 8,9 .…”

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Weyl points and Fermi arcs in a chiral phononic crystal

et al. 2017

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Topological semimetals are materials whose band structure contains touching points that are topologically nontrivial and can host quasiparticle excitations that behave as Dirac or Weyl fermions [1][2][3][4][5][6][7] . These so-called Weyl points not only exist in electronic systems, but can also be found in artificial periodic structures with classical waves, such as electromagnetic waves in photonic crystals [8][9][10][11] and acoustic waves in phononic crystals 12,13 . Due to the lack of spin and a di culty in breaking time-reversal symmetry for sound, however, topological acoustic materials cannot be achieved in the same way as electronic or optical systems. And despite many theoretical predictions 12,13 , experimentally realizing Weyl points in phononic crystals remains challenging. Here, we experimentally realize Weyl points in a chiral phononic crystal system, and demonstrate surface states associated with the Weyl points that are topological in nature, and can host modes that propagate only in one direction. As with their photonic counterparts, chiral phononic crystals bring topological physics to the macroscopic scale.Recently, interest in Weyl semimetals has been growing 1-7 . Weyl semimetals are materials in which the electrons have linear dispersions in all directions while being doubly degenerate at a single point, called the Weyl point, near the Fermi surface in threedimensional (3D) momentum space. In other words, the electrons in Weyl semimetals obey the Weyl equation and thus behave like Weyl fermions. The Weyl point is a source or sink of the Berry curvature flux in momentum space; in other words, it is a magnetic monopole with a topological charge, defined as the Berry curvature flux threading a sphere enclosing the Weyl point with a value of either +1 or −1, corresponding to the chirality of the Weyl fermion. The Weyl point and the associated topological invariants enable Weyl semimetals to exhibit a variety of unusual properties, including robust surface waves (SWs) [14][15][16] and chiral anomaly 17,18 . In addition to the standard Weyl points possessing a point-like Fermi surface (referred to as type-I), another type of Weyl point was more recently recognized, which has a conical Fermi surface (referred to as type-II) 13,[19][20][21] . Since the Weyl point or Weyl cone in Weyl semimetals represents a special dispersion of electrons moving in periodic potentials, the question naturally arises as to whether a similar dispersion or the Weyl point for classical waves propagating in artificial periodic structures exists [8][9][10][11][12][13][22][23][24][25][26][27][28] . Lu et al. were the first to report the existence of Weyl points and the associated one-way SWs in photonic crystals based on double-gyroid structures 8,9 . Weyl points were also observed in photonic crystals fabricated using conventional planar fabrication technology 10,11 . Following the developments of the Weyl photonic crystals, Weyl phononic crystals (PCs) with Weyl points for acoustic waves have also been proposed in graph...

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Photonic Weyl degeneracies in magnetized plasma

Cited by 169 publications

References 44 publications

Field-Selective Anomaly and Chiral Mode Reversal in Type-II Weyl Materials

Field-Selective Anomaly and Chiral Mode Reversal in Type-II Weyl Materials

Weyl and Dirac semimetals in three-dimensional solids

Weyl points and Fermi arcs in a chiral phononic crystal

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