Emergence of topological semimetals in gap closing in semiconductors without inversion symmetry

Murakami, Shuichi; Hirayama, Motoaki; Okugawa, Ryo; Miyake, Takashi

doi:10.1126/sciadv.1602680

Cited by 77 publications

(71 citation statements)

References 48 publications

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“…Although eigenvalues of the C 2 and M symmetries are different in spinless and spinful systems, the expressions for these constraints are the same both in spinless and in spinful cases 60 . As a result, the type-A TNL of the case (II)-(i) crosses the C 2 axis while the type-A TNL of the case (II)-(ii) appears on the M plane, both in spinless and in spinful systems.…”

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confidence: 99%

“…In fact, a similar two-band effective Hamiltonian has been used in spinful WSMs in order to describe band evolutions in Ref. 60, and therefore, here we can extend the analysis in Ref. 60 to some of the spinless TNLSMs as well.…”

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confidence: 99%

“…Therefore, it is important to give a general framework of a phase transition between the spinless topological semimetal phases, as studied in spinful systems 1,8,59 . Moreover, it is recently shown that band evolutions of spinful WSMs are determined by crystallographic symmetries, although the Weyl nodes may arise at generic points 60 . Extending this theory to the TNLSMs helps us to understand the band structures easily.…”

Section: Introductionmentioning

confidence: 99%

“…60, and therefore, here we can extend the analysis in Ref. 60 to some of the spinless TNLSMs as well. In Ref.…”

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confidence: 99%

“…In Ref. 60, it is shown that when two bands touch each other on high-symmetry lines or planes, emergent gapless nodes evolve along the lines and the planes where the two bands have the different eigenvalues. By using these results, we can understand band structures of type-A TNLs.…”

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confidence: 99%

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Universal phase transition and band structures for spinless nodal-line and Weyl semimetals

Okugawa

Murakami

2017

Phys. Rev. B

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We study a general phase transition between spinless topological nodal-line semimetal and Weyl semimetal phases. We classify topological nodal lines into two types based on their positions and shapes, and their phase transitions depends on their types. We show that a topological nodalline semimetal becomes the Weyl semimetal by breaking time-reversal symmetry when the nodal lines enclose time-reversal invariant momenta (type-A nodal lines). We also discuss an effect of crystallographic symmetries determining the band structure of the topological nodal-line semimetals. Thanks to protection by the symmetries, the topological nodal-line semimetals can transition into spinless Weyl semimetals or maintain the nodal lines in many crystals after inversion symmetry is broken.

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confidence: 99%

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confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…60, and therefore, here we can extend the analysis in Ref. 60 to some of the spinless TNLSMs as well. In Ref.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

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Universal phase transition and band structures for spinless nodal-line and Weyl semimetals

Okugawa

Murakami

2017

Phys. Rev. B

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Excellent catalytic performance toward the hydrogen evolution reaction in topological semimetals

Wang

Yang

Wang

et al. 2022

EcoMat

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Topological states of matter and their corresponding properties are classical research topics in condensed matter physics. Quite recently, the application of materials that feature these states has been extended to the field of electrochemical catalysis and become an emerging research topic that is receiving increasing interest. In particular, several recent experimental studies performed on topological semimetals have already revealed high catalytic performance towards hydrogen evolution reaction (HER), strongly promoting acceptance of the fresh concept of the topological catalyst. This emerging concept has experienced rapid developments in the last few years, but these developments have been rarely summarized.Herein, we offer a comprehensive review on the state-of-the-art progress in developing topological catalysts for the HER process through topological semimetals such as Weyl semimetals, Dirac semimetals, nodal line semimetals, etc. The course of development, the general research routes, and the fundamental mechanisms in topological catalysts are also systematically analyzed in this review.

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Dirac and Weyl Semimetals in Sn_1−xIn_xTe

Schmidt

Srivastava

2020

Physica Rapid Research Ltrs

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The recent realization of Weyl fermions in materials [1-10] has received a great deal of attention due to their connection with particle physics, in addition to the promise for technological applications. [11-13] These fermions belong to the topological semimetal class of materials, with accidental degeneracy states around the Fermi level that are protected by topology and symmetry. The protected Weyl fermions present a nonvanishing Chern number around each chiral node. The degenerated chiral points are located in the bulk band structure, connected with surface Fermi arcs. [3-9] There are some conditions to realize Weyl semimetal (WSM) in an inverted bandgap 3D material: the valence and conduction bands must touch each other at the some point of the bulk Brillouin zone (BZ), and a lack of either time reversal or inversion symmetry must occur. With that, the crossing point is symmetry-preserved and pairs of Weyl nodes with opposite chirality are realized. If time reversal and inversion symmetry are preserved in an inverted gap system, the Weyl nodes annihilate, resulting in a Dirac semimetal (DSM) phase. [14-21] In this case the net Chern number is zero; the Dirac crossing is fourfold degenerated and it is not topologically protected, [10] but crystal symmetry can protect the degeneracies if the semimetal character comes from a topological insulator bulk gap closure. Recently, it has been predicted that distinct semimetal topological phases can be obtained by defect engineering with impurities [22] in topological crystalline insulator (TCI) materials. This novel topological class has attracted attention lately [23-29] because their topological sates are protected by crystal symmetry, distinct from Z 2 topological insulators that are protected by time reversal symmetry. Pressure also has been shown to induce topological semimetal phase in TCIs. [30]

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Emergence of topological semimetals in gap closing in semiconductors without inversion symmetry

Abstract: Closing of a band gap of inversion-asymmetric semiconductors always leads either to a Weyl semimetal or to a nodal-line semimetal

Cited by 77 publications

References 48 publications

Universal phase transition and band structures for spinless nodal-line and Weyl semimetals

Universal phase transition and band structures for spinless nodal-line and Weyl semimetals

Excellent catalytic performance toward the hydrogen evolution reaction in topological semimetals

Dirac and Weyl Semimetals in Sn_1−xIn_xTe

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Emergence of topological semimetals in gap closing in semiconductors without inversion symmetry

Abstract: Closing of a band gap of inversion-asymmetric semiconductors always leads either to a Weyl semimetal or to a nodal-line semimetal

Cited by 77 publications

References 48 publications

Universal phase transition and band structures for spinless nodal-line and Weyl semimetals

Universal phase transition and band structures for spinless nodal-line and Weyl semimetals

Excellent catalytic performance toward the hydrogen evolution reaction in topological semimetals

Dirac and Weyl Semimetals in Sn1−xInxTe

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Dirac and Weyl Semimetals in Sn_1−xIn_xTe