Experimental Discovery of Weyl Semimetal TaAs

Lv, Baoliang; Weng, Hongming; Bao, Futing; Wang, Xiaoping; Miao, H.; Ma, Junzhang; Richard, P.; Huang, Xiaochun; Zhao, Lingxiao; Chen, Genfu; Fang, Zhong; Dai, Xi; Qian, Tian; Ding, Hong

doi:10.1103/physrevx.5.031013

Cited by 2,257 publications

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References 41 publications

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“…Note that Eq. (29) demonstrates that the chiral edge modes are allowed for 6 ≥ j ≥ 1 in this case. This accounts for the number of modes observed in the numerical calculation.…”

Section: Modelmentioning

confidence: 76%

Disorder Effect on Chiral Edge Modes and Anomalous Hall Conductance in Weyl Semimetals

Takane

2016

J. Phys. Soc. Jpn.

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Typical Weyl semimetals host chiral surface states and hence show an anomalous Hall response. Although a Weyl semimetal phase is known to be robust against weak disorder, the effect of disorder on chiral states has not been fully clarified so far. We study the behavior of such chiral states in the presence of disorder and its consequences on an anomalous Hall response, focusing on a thin slab of Weyl semimetal with chiral surface states along its edge. It is shown that weak disorder does not disrupt chiral edge states but crucially affects them owing to the renormalization of a mass parameter: the number of chiral edge states changes depending on the strength of disorder. It is also shown that the Hall conductance is quantized when the Fermi level is located near Weyl nodes within a finite-size gap. This quantization of the Hall conductance collapses once the strength of disorder exceeds a critical value, suggesting that it serves as a probe to distinguish a Weyl semimetal phase from a diffusive anomalous Hall metal phase.

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“…Note that Eq. (29) demonstrates that the chiral edge modes are allowed for 6 ≥ j ≥ 1 in this case. This accounts for the number of modes observed in the numerical calculation.…”

Section: Modelmentioning

confidence: 76%

Disorder Effect on Chiral Edge Modes and Anomalous Hall Conductance in Weyl Semimetals

Takane

2016

J. Phys. Soc. Jpn.

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“…On the surface of a Weyl semimetal, the Fermi surface consists of open arcs connecting the projection of bulk Weyl points onto the surface Brillouin zone [2], instead of closed loops. The presence of Fermi arcs on the surface is a remarkable property that directly reflects the nontrivial topology of the bulk, and plays a key role in the experimental identification of Weyl semimetals [32,33,36]. In contrast, as shown by recent theoretical works [18,21,23,24,28,48,49], existing Dirac and nodal line semimetals do not have robust Fermi arcs that are stable against symmetry-allowed perturbations.…”

Section: Introductionmentioning

confidence: 99%

“…The nontrivial topology gives rise to anomalous bulk properties of topological semimetals such as the chiral anomaly [3][4][5]. Several classes of topological semimetals have been theoretically proposed so far, including Weyl, [2,[6][7][8][9][10][11][12][13], Dirac [14][15][16][17] and nodal line semimetals [7,[17][18][19][20][21][22][23][24][25][26][27][28][29][30], some among which have been experimentally observed [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47].Surface states of topological semimetals have attracted much attention. On the surface of a Weyl semimetal, the Fermi surface consists of open ar...…”

mentioning

confidence: 99%

Topological semimetals with helicoid surface states

et al. 2016

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Riemann surfaces are geometric constructions in complex analysis that may represent multi-valued holomorphic functions using multiple sheets of the complex plane. We show that the energy dispersion of surface states in topological semimetals can be represented by Riemann surfaces generated by holomorphic functions in the two-dimensional momentum space, whose constant height contours correspond to Fermi arcs. This correspondence is demonstrated in the recently discovered Weyl semimetals and leads us to predict new types of topological semimetals, whose surface states are represented by double-and quad-helicoid Riemann surfaces. The intersection of multiple helicoids, or the branch cut of the generating function, appears on high-symmetry lines in the surface Brillouin zone, where surface states are guaranteed to be doubly degenerate by a glide reflection symmetry. We predict the heterostructure superlattice [(SrIrO3)2(CaIrO3)2] to be a topological semimetal with double-helicoid Riemann surface states.Introduction The study of topological semimetals [1] has seen rapid progress since the theoretical proposal of a three-dimensional Weyl semimetal in a magnetic phase of pyrochlore iridates [2]. In general, topological semimetals are materials where the conduction and the valence bands cross in the Brillouin zone and the crossing cannot be removed by perturbations preserving certain crystalline symmetry such as the lattice translation. Bloch states in the vicinity of the band crossing possess a nonzero topological index, e.g., the Chern number in case of Weyl semimetals. The nontrivial topology gives rise to anomalous bulk properties of topological semimetals such as the chiral anomaly [3][4][5]. Several classes of topological semimetals have been theoretically proposed so far, including Weyl, [2,[6][7][8][9][10][11][12][13], Dirac [14][15][16][17] and nodal line semimetals [7,[17][18][19][20][21][22][23][24][25][26][27][28][29][30], some among which have been experimentally observed [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47].Surface states of topological semimetals have attracted much attention. On the surface of a Weyl semimetal, the Fermi surface consists of open arcs connecting the projection of bulk Weyl points onto the surface Brillouin zone [2], instead of closed loops. The presence of Fermi arcs on the surface is a remarkable property that directly reflects the nontrivial topology of the bulk, and plays a key role in the experimental identification of Weyl semimetals [32,33,36]. In contrast, as shown by recent theoretical works [18,21,23,24,28,48,49], existing Dirac and nodal line semimetals do not have robust Fermi arcs that are stable against symmetry-allowed perturbations. Therefore, the general condition for protected Fermi arcs and their existence in topological semimetals beyond Weyl remain open questions.In this work, we report the discovery of a new topological semimetal phase in a wide variety of nonsymmorphic crystal structures with the glide reflection sym-

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“…Very recently, the predictions about WSM state in TaAs family 37,38 have been confirmed experimentally. [39][40][41][42] Unlike DSM and WSM whose band crossing points distribute at separate k points in the BZ, for a NLS the crossing points around the Fermi level form a closed loop. Several compounds have been proposed as NLSs, including Mackay-Terrones crystals, 25 Bernal graphite, 43 hyperhoneycomb lattices, 44 and antiperovskite Cu 3 PdN 26,27 and Cu 3 NZn.…”

Section: Introductionmentioning

confidence: 99%

CaTe: a new topological node-line and Dirac semimetal

Du¹,

Tang²,

Wang³

et al. 2017

npj Quant Mater

113

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Combining first-principles calculations and effective model analysis, we predict that CaTe is a topological node-line semimetal in the absence of the spin-orbit coupling. Using a slab model, we obtain the nearly flat drumhead surface state near the Fermi level. When the spin-orbit coupling is included, three node lines will evolve into a pair of Dirac points along the M−R line. These Dirac points are robust and protected by the C 4 rotation symmetry. Once this crystal symmetry is broken, the Dirac points will be eliminated, and the system becomes a strong topological insulator.npj Quantum Materials (2017) 2:3 ; doi:10.1038/s41535-016-0005-4 INTRODUCTIONTopological insulator (TI) has attracted broad interest in the past 10 years. [1][2][3][4][5][6][7] The unique property of TI is that it is an insulator in the bulk but has exotic metallic surface states due to the topological order. More recently, the research on topological states has been extended to three-dimensional (3D) semimetal systems. [8][9][10][11][12] These systems could demonstrate many fascinating phenomena, such as Weyl fermion quantum transport and various Hall effects, [13][14][15][16] consequently become the rising stars of the field. Up to now, three kinds of topological semimetals have been discovered, i.e., 3D Dirac semimetal (DSM), 12,[17][18][19][20][21] Weyl semimetal (WSM), 8,9,22,23 and node-line semimetal (NLS). [24][25][26][27][28][29] The 3D DSM has four-fold degeneracy point, which can be viewed as the kiss of two Weyl fermions with opposite chiralities in the Brillouin zone (BZ). Protected by the crystal symmetry and time reversal symmetry, 3D DSMs can be robust against external perturbations. Several materials have been theoretically predicted to be 3D DSMs 12,17-21 and some of them have already been confirmed by experiments. [30][31][32][33] If one breaks the time reversal symmetry 8,22,23,34 or the inversion symmetry, 35-38 the 3D DSM will evolve into WSM. Very recently, the predictions about WSM state in TaAs family 37,38 have been confirmed experimentally. [39][40][41][42] Unlike DSM and WSM whose band crossing points distribute at separate k points in the BZ, for a NLS the crossing points around the Fermi level form a closed loop. Several compounds have been proposed as NLSs, including Mackay-Terrones crystals, 25 Bernal graphite, 43 hyperhoneycomb lattices, 44 and antiperovskite Cu 3 PdN 26,27 and Cu 3 NZn. 27 In the absence of spin-orbit coupling (SOC), time reversal symmetry together with inversion or mirror symmetry will guarantee the occurrence of node line in 3D BZ for systems with band inversion. [25][26][27]37,45,46 Same with TI and WSM, NLS also has a characteristic surface state, namely, drumhead-like state. 24-29 Such a 2D flat band surface state may become a route to achieve high temperature superconductivity. 47,48 As a result, it is of great impetus to search new NLS.In this study, based on first-principles calculations and effective model analysis, we propose that CaTe in CsCl-type structure is a NLS with drumhea...

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Experimental Discovery of Weyl Semimetal TaAs

Cited by 2,257 publications

References 41 publications

Disorder Effect on Chiral Edge Modes and Anomalous Hall Conductance in Weyl Semimetals

Disorder Effect on Chiral Edge Modes and Anomalous Hall Conductance in Weyl Semimetals

Topological semimetals with helicoid surface states

CaTe: a new topological node-line and Dirac semimetal

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