Observation of Fermi arc surface states in a topological metal

Xu, Su; Liu, Chang; Kushwaha, Satya; Sankar, Raman; Krizan, Jason W.; Belopolski, Ilya; Neupane, Madhab; Bian, Guang; Alidoust, Nasser; Chang, Tay Rong; Jeng, Horng Tay; Huang, Cheng; Tsai, Wei-Feng; Lin, Hsin; Shibayev, Pavel; Chou, F. C.; Cava, R. J.; Hasan, M. Zahid

doi:10.1126/science.1256742

Cited by 678 publications

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“…The surface states near the projection of a Dirac point is hence a superposition of a helicoid and an antihelicoid Riemann surface as shown in Fig.1(c), which cross each other along certain lines, and may have two Fermi arcs [15,16,45]. Yet, if there be no additional symmetry that protects their crossing, hybridization along the crossing lines opens a gap and the double-helicoid structure of the surface dispersion is lost and the Fermi arcs also disappear.…”

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...…”

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confidence: 99%

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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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Section: Introductionmentioning

confidence: 99%

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confidence: 99%

Topological semimetals with helicoid surface states

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“…19,23 The exotic Fermi surface of Na 3 Bi and Cd 3 As 2 was confirmed by the angle-resolved photoemission spectroscopy experiments. [20][21][22][24][25][26] The compound Cd 3 As 2 is of particular interests, as it is stable in air, unlike Na 3 Bi. On the basis of quantum transport measurement, a non-trivial π Berry's phase is obtained, which provides bulk evidence for the existence of 3D Dirac semimetal phase in Cd 3 As 2 .…”

Section: Introductionmentioning

confidence: 99%

“…[18][19][20][21][22][23][24][25][26][27][28][29] As a 3D analogue to graphene, the Fermi surface of the 3D Dirac semimetal only consists of 3D Dirac points with linear energy dispersion in any momentum direction. 19,23 The exotic Fermi surface of Na 3 Bi and Cd 3 As 2 was confirmed by the angle-resolved photoemission spectroscopy experiments.…”

Section: Introductionmentioning

confidence: 99%

Pressure-induced superconductivity in the three-dimensional topological Dirac semimetal Cd3As2

et al. 2016

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The recently discovered Dirac and Weyl semimetals are new members of topological materials. Starting from them, topological superconductivity may be achieved, e.g., by carrier doping or applying pressure. Here we report high-pressure resistance and X-ray diffraction study of the three-dimensional topological Dirac semimetal Cd 3 As 2 . Superconductivity with T c ≈2.0 K is observed at 8.5 GPa. The T c keeps increasing to about 4.0 K at 21.3 GPa, then shows a nearly constant pressure dependence up to the highest pressure 50.9 GPa. The X-ray diffraction measurements reveal a structure phase transition around 3.5 GPa. Our observation of superconductivity in pressurised topological Dirac semimetal Cd 3 As 2 provides a new candidate for topological superconductor, as argued in a recent point contact study and a theoretical work.

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“…Under open boundary conditions (OBC), edge states are observed in Weyl semimetals. In particular, a pair of edge states meets along a line connecting two Weyl points of opposite chiralities, which is called Fermi arc [9,11]. Weyl semimetals are known to exhibit novel transport properties, such as negative magnetoresistance [12][13][14], anomalous Hall effect [15][16][17][18], and chiral magnetic effect [18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Generating controllable type-II Weyl points via periodic driving

Bomantara

Gong

2016

Phys. Rev. B

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Type-II Weyl semimetals are a novel gapless topological phase of matter discovered recently in 2015. Similar to normal (type-I) Weyl semimetals, type-II Weyl semimetals consist of isolated band touching points. However, unlike type-I Weyl semimetals which have a linear energy dispersion around the band touching points forming a three dimensional (3D) Dirac cone, type-II Weyl semimetals have a tilted cone-like structure around the band touching points. This leads to various novel physical properties that are different from type-I Weyl semimetals. In order to study further the properties of type-II Weyl semimetals and perhaps realize them for future applications, generating controllable type-II Weyl semimetals is desirable. In this paper, we propose a way to generate a type-II Weyl semimetal via a generalized Harper model interacting with a harmonic driving field. When the field is treated classically, we find that only type-I Weyl points emerge.However, by treating the field quantum mechanically, some of these type-I Weyl points may turn into type-II Weyl points. Moreover, by tuning the coupling strength, it is possible to control the tilt of the Weyl points and the energy difference between two Weyl points, which makes it possible to generate a pair of mixed Weyl points of type-I and type-II. We also discuss how to physically distinguish these two types of Weyl points in the framework of our model via the Landau level structures in the presence of an artificial magnetic field. The results are of general interest to quantum optics as well as ongoing studies of Floquet topological phases.

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Observation of Fermi arc surface states in a topological metal

Cited by 678 publications

References 37 publications

Topological semimetals with helicoid surface states

Topological semimetals with helicoid surface states

Pressure-induced superconductivity in the three-dimensional topological Dirac semimetal Cd3As2

Generating controllable type-II Weyl points via periodic driving

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