Momentum-space structure of surface states in a topological semimetal with a nexus point of Dirac lines

Hyart, Timo; Heikkilä, Tero T.

doi:10.1103/physrevb.93.235147

Cited by 63 publications

(37 citation statements)

References 98 publications

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“…3(a)). Previously, TPs have been discussed in the context of Bernal-stacked graphite with neglected SOI [57][58][59], spin-1 quasiparticles in two dimensions [60,61] and strained HgTe [62]. The TP we find is furthermore accompanied by four Weyl nodal lines [63] in the vertical mirror planes, degenerate lines between the second and third band in Fig.…”

supporting

confidence: 49%

Topological Phases inInAs1−xSbx: From Novel Topological Semimetal to Majorana Wire

et al. 2016

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Superconductor proximitized one-dimensional semiconductor nanowires with strong spin-orbit interaction (SOI) are at this time the most promising candidates for the realization of topological quantum information processing. In current experiments the SOI originates predominantly from extrinsic fields, induced by finite size effects and applied gate voltages. The dependence of the topological transition in these devices on microscopic details makes scaling to a large number of devices difficult unless a material with dominant intrinsic bulk SOI is used. Here we show that wires made of certain ordered alloys InAs1−xSbx have spin splittings up to 20 times larger than those reached in pristine InSb wires. In particular, we show this for a stable ordered CuPt-structure at x = 0.5, which has an inverted band ordering and realizes a novel type of a topological semimetal with triple degeneracy points in the bulk spectrum that produce topological surface Fermi arcs. Experimentally achievable strains can drive this compound either into a topological insulator phase, or restore the normal band ordering making the CuPt-ordered InAs0.5Sb0.5 a semiconductor with a large intrinsic linear in k bulk spin splitting.In recent years, a range of topological phases have been realized in materials, ranging from topological insulators [1, 2] (TIs) and semimetals [3][4][5][6] (TSMs) to superconductors [7, 8] (TSCs). The non-trivial topology of the ground state wavefunctions in these phases causes a variety of phenomena in such materials ranging from topologically protected metallic surface or edge states in TIs [1, 2] and Fermi arcs and anomalous magnetotransport in TSMs [4,[9][10][11], to quasiparticles with nonAbelian particle statistics [12][13][14][15][16][17][18][19] in TSCs, which could be used for topological quantum computation [20,21].Arguably the simplest scheme for realizing nonAbelian statistics in a solid-state device is based on manipulating Majorana zero modes (MZMs) in networks of semiconductor wires. MZMs were predicted to appear at the ends of spin-orbit coupled wires subject to a parallel magnetic field, proximity coupled to an s-wave superconductor. Experimental observations, consistent with the theory, were reported for InAs and InSb zincblende nanowires [19,[22][23][24].The stability of MZMs in such a setup depends greatly on the size of the spin-orbit splitting (SOS) of the conduction band. SOS is very small in bulk zincblende semiconductors [25] and the realization of the MZMs thus relies on the externally induced Rashba SOS [26], which is estimated to be of the order of 1 meV [27,28]. This value is very small compared to the bulk splitting in some recently discovered compounds [29][30][31][32]. However, most of these materials are not suitable for realizing MZMs within the above scenario, while for others such experiments appear to be challenging. It is thus desirable to understand if large values of bulk SOS can be achieved within the III-V materials class, used in most experiments at this time. A bulk SOS dom...

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confidence: 49%

Topological Phases inInAs1−xSbx: From Novel Topological Semimetal to Majorana Wire

et al. 2016

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“…The presence of nodal lines with nontrivial Berry phase, as is the case for type B, is generally associated with the appearance of surface states [26,27]. The merging and subsequent annihilation of nodal lines is similar to the nexus point discussed in the context of 3 He-A and Bernal-stacked graphite with neglected spin-orbit coupling (SOC) [28][29][30][31]. We stress, however, that the scenarios discussed in the present work take full account of SOC.…”

Section: Classification Of Symmorphic Triple Pointsmentioning

confidence: 43%

Triple Point Topological Metals

et al. 2016

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Topologically protected fermionic quasiparticles appear in metals, where band degeneracies occur at the Fermi level, dictated by the band structure topology. While in some metals these quasiparticles are direct analogues of elementary fermionic particles of the relativistic quantum field theory, other metals can have symmetries that give rise to quasiparticles, fundamentally different from those known in high-energy physics. Here, we report on a new type of topological quasiparticles-triple point fermions-realized in metals with symmorphic crystal structure, which host crossings of three bands in the vicinity of the Fermi level protected by point group symmetries. We find two topologically different types of triple point fermions, both distinct from any other topological quasiparticles reported to date. We provide examples of existing materials that host triple point fermions of both types and discuss a variety of physical phenomena associated with these quasiparticles, such as the occurrence of topological surface Fermi arcs, transport anomalies, and topological Lifshitz transitions.

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“…The Weyl points carry nonzero Chern numbers, i.e., topological chiral charges, C = ±1, which induce unusual physical phenomena, such as chiral anomaly effects and helical surface states. In addition to the twofold-degenerate Weyl points, there are a variety of higherorder degenerate points in topological semimetals, where the electronic excitations form different types of fermionic quasiparticles [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30], such as the fourfolddegenerate Dirac points in Na3Bi and Cd3As2 [14][15][16][17] and the threefold-degenerate points in the WC-structure materials [23][24][25][26][27]. However, these degenerate points do not carry nonzero chiral charges, so the Dirac fermions and three-component fermions in these materials are not chiral.…”

Section: Introductionmentioning

confidence: 99%

Chiral fermion reversal in chiral crystals

Li¹,

Xu²,

Rao³

et al. 2019

Nat Commun

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In materials chiral fermions such as Weyl fermions are characterized by nonzero chiral charges, which are singular points of Berry curvature in momentum space. Recently, new types of chiral fermions beyond Weyl fermions have been discovered in structurally chiral crystals CoSi, RhSi and PtAl. Here, we have synthesized RhSn single crystals, which have opposite structural chirality to the CoSi crystals we previously studied. Using angle-resolved photoemission spectroscopy, we show that the bulk electronic structures of RhSn are consistent with the band calculations and observe evident surface Fermi arcs and helical surface bands, confirming the existence of chiral fermions in RhSn. It is noteworthy that the helical surface bands of the RhSn and CoSi crystals have opposite handedness, meaning that the chiral fermions are reversed in the crystals of opposite structural chirality. Our discovery establishes a direct connection between chiral fermions in momentum space and chiral lattices in real space.

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Momentum-space structure of surface states in a topological semimetal with a nexus point of Dirac lines

Cited by 63 publications

References 98 publications

Topological Phases inInAs1−xSbx: From Novel Topological Semimetal to Majorana Wire

Topological Phases inInAs1−xSbx: From Novel Topological Semimetal to Majorana Wire

Triple Point Topological Metals

Chiral fermion reversal in chiral crystals

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