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Liu, Cheng-Cheng; Zhou, Jin-Jian; Yao, Yugui; Zhang, Fan

doi:10.1103/physrevlett.116.066801

Cited by 88 publications

(92 citation statements)

References 61 publications

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“…Till now several materials have been predicted to be near the critical point, such as CdTe/GdTe quantum well with specific thickness 15 , ZrTe 5 19–22 , Ca 2 PtO 4 23 , Au 2 Pb 24, 25 , Bi 4 X 4 26, 27 , Bi 2 Te 2 Se 28 and so on. Most of them have been studied intensively.…”

Section: Introductionmentioning

confidence: 99%

Electronic structure of SrSn2As2 near the topological critical point

Rong

Nie

et al. 2017

Sci Rep

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Topological materials with exotic quantum properties are promising candidates for quantum spin electronics. Different classes of topological materials, including Weyl semimetal, topological superconductor, topological insulator and Axion insulator, etc., can be connected to each other via quantum phase transition. For example, it is believed that a trivial band insulator can be twisted into topological phase by increasing spin-orbital coupling or changing the parameters of crystal lattice. With the results of LDA calculation and measurement by angle-resolved photoemission spectroscopy (ARPES), we demonstrate in this work that the electronic structure of SrSn2As2 single crystal has the texture of band inversion near the critical point. The results indicate the possibility of realizing topological quantum phase transition in SrSn2As2 single crystal and obtaining different exotic quantum states.

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Section: Introductionmentioning

confidence: 99%

Electronic structure of SrSn2As2 near the topological critical point

Rong

Nie

et al. 2017

Sci Rep

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“…In spite of the enormous amount of research, one fundamental property of Bi has been controversial: its electronic topology. Because of its huge spin-orbit coupling (SOC) [14], Bi has also been a central element in designing topological materials such as Bi 1−x Sb x , Bi 2 Se 3 , Na 3 Bi, and β-Bi 4 I 4 [15][16][17][18][19]. A combination of SOC and several symmetries produces topologically protected electronic states with inherent spin splitting.…”

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confidence: 99%

Proving Nontrivial Topology of Pure Bismuth by Quantum Confinement

et al. 2016

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The topology of pure Bi is controversial because of its very small (∼10 meV) band gap. Here we perform high-resolution angle-resolved photoelectron spectroscopy measurements systematically on 14−202 bilayer Bi films. Using high-quality films, we succeed in observing quantized bulk bands with energy separations down to ∼10 meV. Detailed analyses on the phase shift of the confined wave functions precisely determine the surface and bulk electronic structures, which unambiguously show nontrivial topology. The present results not only prove the fundamental property of Bi but also introduce a capability of the quantum-confinement approach. [5]. Even now, numbers of novel quantum phenomena have been intensively reported on this system [6][7][8][9][10][11][12][13]. In spite of the enormous amount of research, one fundamental property of Bi has been controversial: its electronic topology. Because of its huge spin-orbit coupling (SOC) [14], Bi has also been a central element in designing topological materials such as Bi 1−x Sb x , Bi 2 Se 3 , Na 3 Bi, and β-Bi 4 I 4 [15][16][17][18][19]. A combination of SOC and several symmetries produces topologically protected electronic states with inherent spin splitting. Despite the essential role in topological studies, a pure Bi crystal itself had long been believed topologically trivial based on several calculations [20][21][22][23][24][25][26], which had been considered to agree with transport [27] and angleresolved photoelectron spectroscopy (ARPES) measurements [22,28,29]. However, a recent high-resolution ARPES result suggests the surface bands are actually different from previously calculated ones and Bi possesses a nontrivial topology [30,31]. New transport measurements also imply the presence of topologically protected surface states [32,33].Nevertheless, the recent ARPES result has not yet been conclusive because it lacks clear peaks of bulk bands [30,31]. In principle, surface-normal bulk dispersions can be measured by changing the incident photon energy, where the momentum resolution is determined from the uncertainty relation ∆z · ∆k z ≥ 1/2 (Ref.[34]). (∆z is an escape depth of photoelectrons.) However, the Dirac dispersion of Bi is so sharp against this resolution that hν-dependent spectra show no clear peak [29][30][31]. This is a serious problem because Bi has a very small (∼10 meV [21,26]) band gap and a slight energy shift in bulk bands can easily transform a nontrivial case [ Fig. 1(d)] into a trivial case [ Fig. 1(e)]. In short, to unambiguously identify the topology of Bi, one must precisely determine both the surface and bulk electronic structures. One promising approach is using a thin film geometry, where quantumwell state (QWS) subbands are formed inside bulk band projections [35,36]. Although QWSs originate from bulk states, they possess a two-dimensional character and can be clearly observed in ARPES measurements.In this Letter, we performed high-resolution ARPES

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“…Both first-principles electronic structure calculations and angle-resolved photoemission spectroscopy (ARPES) studies demonstrate that β-Bi4I4 is at the boundary of a strongweak topological insulator phases and a trivial insulator one [4]. Pressure or chemical doping could drive the material in one or another phase inducing a topological phase transition [4,8] as already observed in β-As2Te3 [9] and PbTe [10]. Moreover, pressure can efficiently modify the small bandgap and the band structure of TIs, enhancing the thermoelectric properties, without introducing additional disorder like chemical doping would do [11].…”

Section: Introductionmentioning

confidence: 99%

Pressure effect and superconductivity in theβ−Bi4I4topological insulator

et al. 2017

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We report a detailed study of the transport coefficients of β-Bi4I4 quasi-one dimensional topological insulator. Electrical resistivity, thermoelectric power, thermal conductivity and Hall coefficient measurements are consistent with the possible appearance of a charge density wave order at low temperatures. Both electrons and holes contribute to the conduction in β-Bi4I4 and the dominant type of charge carrier changes with temperature as a consequence of temperature-dependent carrier densities and mobilities. Measurements of resistivity and Seebeck coefficient under hydrostatic pressure up to 2 GPa show a shift of the charge density wave order to higher temperatures suggesting a strongly one-dimensional character at ambient pressure. Surprisingly, superconductivity is induced in β-Bi4I4 above 10 GPa with c T of 4.0 K which is slightly decreasing upon increasing the pressure up to 20 GPa. Chemical characterisation of the pressure-treated samples shows amorphization of β-Bi4I4 under pressure and rules out decomposition into Bi and BiI3 at room-temperature conditions.

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Weak Topological Insulators and Composite Weyl Semimetals:β−Bi4X4(X

Cited by 88 publications

References 61 publications

Electronic structure of SrSn2As2 near the topological critical point

Electronic structure of SrSn2As2 near the topological critical point

Proving Nontrivial Topology of Pure Bismuth by Quantum Confinement

Pressure effect and superconductivity in theβ−Bi4I4topological insulator

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