The Experts below are selected from a list of 22935 Experts worldwide ranked by ideXlab platform
Madhab Neupane - One of the best experts on this subject based on the ideXlab platform.
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discovery of a new type of topological weyl fermion semimetal state in moxw1 xte2
Nature Communications, 2016Co-Authors: Ilya Belopolski, Nasser Alidoust, Guang Bian, Guoqing Chang, Daniel S. Sanchez, Yukiaki Ishida, Tay Rong Chang, Hao Zheng, Xingchen Pan, Madhab NeupaneAbstract:The recent discovery of a Weyl semimetal in TaAs offers the first Weyl fermion observed in nature and dramatically broadens the classification of topological phases. However, in TaAs it has proven challenging to study the rich transport phenomena arising from emergent Weyl fermions. The series MoxW1-xTe2 are inversion-breaking, layered, tunable Semimetals already under study as a promising platform for new electronics and recently proposed to host Type II, or strongly Lorentz-violating, Weyl fermions. Here we report the discovery of a Weyl semimetal in MoxW1-xTe2 at x=25%. We use pump-probe angle-resolved photoemission spectroscopy (pump-probe ARPES) to directly observe a topological Fermi arc above the Fermi level, demonstrating a Weyl semimetal. The excellent agreement with calculation suggests that MoxW1-xTe2 is a Type II Weyl semimetal. We also find that certain Weyl points are at the Fermi level, making MoxW1-xTe2 a promising platform for transport and optics experiments on Weyl Semimetals.
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fermi surface interconnectivity and topology in weyl fermion Semimetals taas tap nbas and nbp
Physical Review B, 2015Co-Authors: Chicheng Lee, Ilya Belopolski, Nasser Alidoust, Madhab Neupane, Guang Bian, Guoqing Chang, Shinming Huang, Daniel S. Sanchez, Hao ZhengAbstract:The family of binary compounds including TaAs, TaP, NbAs, and NbP was recently discovered as the first realization of Weyl Semimetals. In order to develop a comprehensive description of the charge carriers in these Weyl Semimetals, we performed detailed and systematic electronic band structure calculations which reveal the nature of Fermi surfaces and their complex interconnectivity in TaAs, TaP, NbAs, and NbP. Our work reports a comparative and comprehensive study of Fermi surface topology and band structure details of all known members of the Weyl semimetal family and hence provides the fundamental knowledge for realizing the many predicted exotic topological quantum physics of Weyl Semimetals based on the TaAs class of materials.
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a weyl fermion semimetal with surface fermi arcs in the transition metal monopnictide taas class
Nature Communications, 2015Co-Authors: Shinming Huang, Ilya Belopolski, Nasser Alidoust, Madhab Neupane, Guang Bian, Guoqing Chang, Chicheng Lee, B WangAbstract:Weyl fermions are massless chiral fermions that play an important role in quantum field theory but have never been observed as fundamental particles. A Weyl semimetal is an unusual crystal that hosts Weyl fermions as quasiparticle excitations and features Fermi arcs on its surface. Such a semimetal not only provides a condensed matter realization of the anomalies in quantum field theories but also demonstrates the topological classification beyond the gapped topological insulators. Here, we identify a topological Weyl semimetal state in the transition metal monopnictide materials class. Our first-principles calculations on TaAs reveal its bulk Weyl fermion cones and surface Fermi arcs. Our results show that in the TaAs-type materials the Weyl semimetal state does not depend on fine-tuning of chemical composition or magnetic order, which opens the door for the experimental realization of Weyl Semimetals and Fermi arc surface states in real materials. Proposals for the realization of Weyl Semimetals, topologically non-trivial materials which host Weyl fermion quasiparticles, have faced demanding experimental requirements. Here, the authors predict such a state in stoichiometric TaAs, arising due to the breaking of inversion symmetry.
Guoqing Chang - One of the best experts on this subject based on the ideXlab platform.
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magnetic and noncentrosymmetric weyl fermion Semimetals in the r alge family of compounds r rare earth
Physical Review B, 2018Co-Authors: Guoqing Chang, Ilya Belopolski, Nasser Alidoust, Guang Bian, Shinming Huang, Daniel S. Sanchez, Bahadur Singh, Chuanghan Hsu, Hao ZhengAbstract:Weyl Semimetals are novel topological conductors that host Weyl fermions as emergent quasiparticles. In this Rapid Communication, we propose a new type of Weyl semimetal state that breaks both time-reversal symmetry and inversion symmetry in the $R\mathrm{AlGe}$ ($R=\mathrm{rare}\ensuremath{-}\mathrm{earth}$) family. Compared to previous predictions of magnetic Weyl semimetal candidates, the prediction of Weyl nodes in $R\mathrm{AlGe}$ is more robust and less dependent on the details of the magnetism because the Weyl nodes are generated already by the inversion breaking and the ferromagnetism acts as a simple Zeeman coupling that shifts the Weyl nodes in $k$ space. Moreover, $R\mathrm{AlGe}$ offers remarkable tunability, which covers all varieties of Weyl Semimetals including type I, type II, inversion breaking, and time-reversal breaking, depending on a suitable choice of the rare-earth elements. Furthermore, the unique noncentrosymmetric and ferromagnetic Weyl semimetal state in $R\mathrm{AlGe}$ enables the generation of spin currents.
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Signatures of a time-reversal symmetric Weyl semimetal with only four Weyl points
Nature communications, 2017Co-Authors: Ilya Belopolski, Guoqing Chang, Daniel S. Sanchez, Yukiaki Ishida, Tay Rong Chang, Songtian S. Zhang, Hao Zheng, Guang BianAbstract:Through intense research on Weyl Semimetals during the past few years, we have come to appreciate that typical Weyl Semimetals host many Weyl points. Nonetheless, the minimum nonzero number of Weyl points allowed in a time-reversal invariant Weyl semimetal is four. Realizing such a system is of fundamental interest and may simplify transport experiments. Recently, it was predicted that TaIrTe4 realizes a minimal Weyl semimetal. However, the Weyl points and Fermi arcs live entirely above the Fermi level, making them inaccessible to conventional angle-resolved photoemission spectroscopy (ARPES). Here, we use pump-probe ARPES to directly access the band structure above the Fermi level in TaIrTe4. We observe signatures of Weyl points and topological Fermi arcs. Combined with ab initio calculation, our results show that TaIrTe4 is a Weyl semimetal with the minimum number of four Weyl points. Our work provides a simpler platform for accessing exotic transport phenomena arising in Weyl Semimetals.Weyl Semimetals are interesting because they are characterized by topological invariants, but specific examples discovered to date tend to have complicated band structures with many Weyl points. Here, the authors show that TaIrTe4 has only four Weyl points, the minimal number required by time-reversal symmetry.
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room temperature magnetic topological weyl fermion and nodal line semimetal states in half metallic heusler co 2 tix x si ge or sn
Scientific Reports, 2016Co-Authors: Guoqing Chang, Ilya Belopolski, Nasser Alidoust, Guang Bian, Daniel S. Sanchez, Songtian S. Zhang, Hao Zheng, Bahadur Singh, Chuanghan Hsu, Hsin LinAbstract:Topological Semimetals (TSMs) including Weyl Semimetals and nodal-line Semimetals are expected to open the next frontier of condensed matter and materials science. Although the first inversion breaking Weyl semimetal was recently discovered in TaAs, its magnetic counterparts, i.e., the time-reversal breaking Weyl and nodal line Semimetals, remain elusive. They are predicted to exhibit exotic properties distinct from the inversion breaking TSMs including TaAs. In this paper, we identify the magnetic topological semimetal states in the ferromagnetic half-metal compounds Co2TiX (X = Si, Ge, or Sn) with Curie temperatures higher than 350 K. Our first-principles band structure calculations show that, in the absence of spin-orbit coupling, Co2TiX features three topological nodal lines. The inclusion of spin-orbit coupling gives rise to Weyl nodes, whose momentum space locations can be controlled as a function of the magnetization direction. Our results not only open the door for the experimental realization of topological semimetal states in magnetic materials at room temperature, but also suggest potential applications such as unusual anomalous Hall effect in engineered monolayers of the Co2TiX compounds at high temperature.
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discovery of a new type of topological weyl fermion semimetal state in moxw1 xte2
Nature Communications, 2016Co-Authors: Ilya Belopolski, Nasser Alidoust, Guang Bian, Guoqing Chang, Daniel S. Sanchez, Yukiaki Ishida, Tay Rong Chang, Hao Zheng, Xingchen Pan, Madhab NeupaneAbstract:The recent discovery of a Weyl semimetal in TaAs offers the first Weyl fermion observed in nature and dramatically broadens the classification of topological phases. However, in TaAs it has proven challenging to study the rich transport phenomena arising from emergent Weyl fermions. The series MoxW1-xTe2 are inversion-breaking, layered, tunable Semimetals already under study as a promising platform for new electronics and recently proposed to host Type II, or strongly Lorentz-violating, Weyl fermions. Here we report the discovery of a Weyl semimetal in MoxW1-xTe2 at x=25%. We use pump-probe angle-resolved photoemission spectroscopy (pump-probe ARPES) to directly observe a topological Fermi arc above the Fermi level, demonstrating a Weyl semimetal. The excellent agreement with calculation suggests that MoxW1-xTe2 is a Type II Weyl semimetal. We also find that certain Weyl points are at the Fermi level, making MoxW1-xTe2 a promising platform for transport and optics experiments on Weyl Semimetals.
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room temperature magnetic topological weyl fermion and nodal line semimetal states in half metallic heusler co2tix x si ge or sn
Scientific Reports, 2016Co-Authors: Guoqing Chang, Ilya Belopolski, Nasser Alidoust, Guang Bian, Daniel S. Sanchez, Hao Zheng, Bahadur Singh, Chuanghan Hsu, Suyang Xu, Songtian S. ZhangAbstract:Topological Semimetals (TSMs) including Weyl Semimetals and nodal-line Semimetals are expected to open the next frontier of condensed matter and materials science. Although the first inversion breaking Weyl semimetal was recently discovered in TaAs, its magnetic counterparts, i.e., the time-reversal breaking Weyl and nodal line Semimetals, remain elusive. They are predicted to exhibit exotic properties distinct from the inversion breaking TSMs including TaAs. In this paper, we identify the magnetic topological semimetal states in the ferromagnetic half-metal compounds Co2TiX (X = Si, Ge, or Sn) with Curie temperatures higher than 350 K. Our first-principles band structure calculations show that, in the absence of spin-orbit coupling, Co2TiX features three topological nodal lines. The inclusion of spin-orbit coupling gives rise to Weyl nodes, whose momentum space locations can be controlled as a function of the magnetization direction. Our results not only open the door for the experimental realization of topological semimetal states in magnetic materials at room temperature, but also suggest potential applications such as unusual anomalous Hall effect in engineered monolayers of the Co2TiX compounds at high temperature.
Guang Bian - One of the best experts on this subject based on the ideXlab platform.
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magnetic and noncentrosymmetric weyl fermion Semimetals in the r alge family of compounds r rare earth
Physical Review B, 2018Co-Authors: Guoqing Chang, Ilya Belopolski, Nasser Alidoust, Guang Bian, Shinming Huang, Daniel S. Sanchez, Bahadur Singh, Chuanghan Hsu, Hao ZhengAbstract:Weyl Semimetals are novel topological conductors that host Weyl fermions as emergent quasiparticles. In this Rapid Communication, we propose a new type of Weyl semimetal state that breaks both time-reversal symmetry and inversion symmetry in the $R\mathrm{AlGe}$ ($R=\mathrm{rare}\ensuremath{-}\mathrm{earth}$) family. Compared to previous predictions of magnetic Weyl semimetal candidates, the prediction of Weyl nodes in $R\mathrm{AlGe}$ is more robust and less dependent on the details of the magnetism because the Weyl nodes are generated already by the inversion breaking and the ferromagnetism acts as a simple Zeeman coupling that shifts the Weyl nodes in $k$ space. Moreover, $R\mathrm{AlGe}$ offers remarkable tunability, which covers all varieties of Weyl Semimetals including type I, type II, inversion breaking, and time-reversal breaking, depending on a suitable choice of the rare-earth elements. Furthermore, the unique noncentrosymmetric and ferromagnetic Weyl semimetal state in $R\mathrm{AlGe}$ enables the generation of spin currents.
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Signatures of a time-reversal symmetric Weyl semimetal with only four Weyl points
Nature communications, 2017Co-Authors: Ilya Belopolski, Guoqing Chang, Daniel S. Sanchez, Yukiaki Ishida, Tay Rong Chang, Songtian S. Zhang, Hao Zheng, Guang BianAbstract:Through intense research on Weyl Semimetals during the past few years, we have come to appreciate that typical Weyl Semimetals host many Weyl points. Nonetheless, the minimum nonzero number of Weyl points allowed in a time-reversal invariant Weyl semimetal is four. Realizing such a system is of fundamental interest and may simplify transport experiments. Recently, it was predicted that TaIrTe4 realizes a minimal Weyl semimetal. However, the Weyl points and Fermi arcs live entirely above the Fermi level, making them inaccessible to conventional angle-resolved photoemission spectroscopy (ARPES). Here, we use pump-probe ARPES to directly access the band structure above the Fermi level in TaIrTe4. We observe signatures of Weyl points and topological Fermi arcs. Combined with ab initio calculation, our results show that TaIrTe4 is a Weyl semimetal with the minimum number of four Weyl points. Our work provides a simpler platform for accessing exotic transport phenomena arising in Weyl Semimetals.Weyl Semimetals are interesting because they are characterized by topological invariants, but specific examples discovered to date tend to have complicated band structures with many Weyl points. Here, the authors show that TaIrTe4 has only four Weyl points, the minimal number required by time-reversal symmetry.
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room temperature magnetic topological weyl fermion and nodal line semimetal states in half metallic heusler co 2 tix x si ge or sn
Scientific Reports, 2016Co-Authors: Guoqing Chang, Ilya Belopolski, Nasser Alidoust, Guang Bian, Daniel S. Sanchez, Songtian S. Zhang, Hao Zheng, Bahadur Singh, Chuanghan Hsu, Hsin LinAbstract:Topological Semimetals (TSMs) including Weyl Semimetals and nodal-line Semimetals are expected to open the next frontier of condensed matter and materials science. Although the first inversion breaking Weyl semimetal was recently discovered in TaAs, its magnetic counterparts, i.e., the time-reversal breaking Weyl and nodal line Semimetals, remain elusive. They are predicted to exhibit exotic properties distinct from the inversion breaking TSMs including TaAs. In this paper, we identify the magnetic topological semimetal states in the ferromagnetic half-metal compounds Co2TiX (X = Si, Ge, or Sn) with Curie temperatures higher than 350 K. Our first-principles band structure calculations show that, in the absence of spin-orbit coupling, Co2TiX features three topological nodal lines. The inclusion of spin-orbit coupling gives rise to Weyl nodes, whose momentum space locations can be controlled as a function of the magnetization direction. Our results not only open the door for the experimental realization of topological semimetal states in magnetic materials at room temperature, but also suggest potential applications such as unusual anomalous Hall effect in engineered monolayers of the Co2TiX compounds at high temperature.
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discovery of a new type of topological weyl fermion semimetal state in moxw1 xte2
Nature Communications, 2016Co-Authors: Ilya Belopolski, Nasser Alidoust, Guang Bian, Guoqing Chang, Daniel S. Sanchez, Yukiaki Ishida, Tay Rong Chang, Hao Zheng, Xingchen Pan, Madhab NeupaneAbstract:The recent discovery of a Weyl semimetal in TaAs offers the first Weyl fermion observed in nature and dramatically broadens the classification of topological phases. However, in TaAs it has proven challenging to study the rich transport phenomena arising from emergent Weyl fermions. The series MoxW1-xTe2 are inversion-breaking, layered, tunable Semimetals already under study as a promising platform for new electronics and recently proposed to host Type II, or strongly Lorentz-violating, Weyl fermions. Here we report the discovery of a Weyl semimetal in MoxW1-xTe2 at x=25%. We use pump-probe angle-resolved photoemission spectroscopy (pump-probe ARPES) to directly observe a topological Fermi arc above the Fermi level, demonstrating a Weyl semimetal. The excellent agreement with calculation suggests that MoxW1-xTe2 is a Type II Weyl semimetal. We also find that certain Weyl points are at the Fermi level, making MoxW1-xTe2 a promising platform for transport and optics experiments on Weyl Semimetals.
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room temperature magnetic topological weyl fermion and nodal line semimetal states in half metallic heusler co2tix x si ge or sn
Scientific Reports, 2016Co-Authors: Guoqing Chang, Ilya Belopolski, Nasser Alidoust, Guang Bian, Daniel S. Sanchez, Hao Zheng, Bahadur Singh, Chuanghan Hsu, Suyang Xu, Songtian S. ZhangAbstract:Topological Semimetals (TSMs) including Weyl Semimetals and nodal-line Semimetals are expected to open the next frontier of condensed matter and materials science. Although the first inversion breaking Weyl semimetal was recently discovered in TaAs, its magnetic counterparts, i.e., the time-reversal breaking Weyl and nodal line Semimetals, remain elusive. They are predicted to exhibit exotic properties distinct from the inversion breaking TSMs including TaAs. In this paper, we identify the magnetic topological semimetal states in the ferromagnetic half-metal compounds Co2TiX (X = Si, Ge, or Sn) with Curie temperatures higher than 350 K. Our first-principles band structure calculations show that, in the absence of spin-orbit coupling, Co2TiX features three topological nodal lines. The inclusion of spin-orbit coupling gives rise to Weyl nodes, whose momentum space locations can be controlled as a function of the magnetization direction. Our results not only open the door for the experimental realization of topological semimetal states in magnetic materials at room temperature, but also suggest potential applications such as unusual anomalous Hall effect in engineered monolayers of the Co2TiX compounds at high temperature.
Ilya Belopolski - One of the best experts on this subject based on the ideXlab platform.
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magnetic and noncentrosymmetric weyl fermion Semimetals in the r alge family of compounds r rare earth
Physical Review B, 2018Co-Authors: Guoqing Chang, Ilya Belopolski, Nasser Alidoust, Guang Bian, Shinming Huang, Daniel S. Sanchez, Bahadur Singh, Chuanghan Hsu, Hao ZhengAbstract:Weyl Semimetals are novel topological conductors that host Weyl fermions as emergent quasiparticles. In this Rapid Communication, we propose a new type of Weyl semimetal state that breaks both time-reversal symmetry and inversion symmetry in the $R\mathrm{AlGe}$ ($R=\mathrm{rare}\ensuremath{-}\mathrm{earth}$) family. Compared to previous predictions of magnetic Weyl semimetal candidates, the prediction of Weyl nodes in $R\mathrm{AlGe}$ is more robust and less dependent on the details of the magnetism because the Weyl nodes are generated already by the inversion breaking and the ferromagnetism acts as a simple Zeeman coupling that shifts the Weyl nodes in $k$ space. Moreover, $R\mathrm{AlGe}$ offers remarkable tunability, which covers all varieties of Weyl Semimetals including type I, type II, inversion breaking, and time-reversal breaking, depending on a suitable choice of the rare-earth elements. Furthermore, the unique noncentrosymmetric and ferromagnetic Weyl semimetal state in $R\mathrm{AlGe}$ enables the generation of spin currents.
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Signatures of a time-reversal symmetric Weyl semimetal with only four Weyl points
Nature communications, 2017Co-Authors: Ilya Belopolski, Guoqing Chang, Daniel S. Sanchez, Yukiaki Ishida, Tay Rong Chang, Songtian S. Zhang, Hao Zheng, Guang BianAbstract:Through intense research on Weyl Semimetals during the past few years, we have come to appreciate that typical Weyl Semimetals host many Weyl points. Nonetheless, the minimum nonzero number of Weyl points allowed in a time-reversal invariant Weyl semimetal is four. Realizing such a system is of fundamental interest and may simplify transport experiments. Recently, it was predicted that TaIrTe4 realizes a minimal Weyl semimetal. However, the Weyl points and Fermi arcs live entirely above the Fermi level, making them inaccessible to conventional angle-resolved photoemission spectroscopy (ARPES). Here, we use pump-probe ARPES to directly access the band structure above the Fermi level in TaIrTe4. We observe signatures of Weyl points and topological Fermi arcs. Combined with ab initio calculation, our results show that TaIrTe4 is a Weyl semimetal with the minimum number of four Weyl points. Our work provides a simpler platform for accessing exotic transport phenomena arising in Weyl Semimetals.Weyl Semimetals are interesting because they are characterized by topological invariants, but specific examples discovered to date tend to have complicated band structures with many Weyl points. Here, the authors show that TaIrTe4 has only four Weyl points, the minimal number required by time-reversal symmetry.
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room temperature magnetic topological weyl fermion and nodal line semimetal states in half metallic heusler co 2 tix x si ge or sn
Scientific Reports, 2016Co-Authors: Guoqing Chang, Ilya Belopolski, Nasser Alidoust, Guang Bian, Daniel S. Sanchez, Songtian S. Zhang, Hao Zheng, Bahadur Singh, Chuanghan Hsu, Hsin LinAbstract:Topological Semimetals (TSMs) including Weyl Semimetals and nodal-line Semimetals are expected to open the next frontier of condensed matter and materials science. Although the first inversion breaking Weyl semimetal was recently discovered in TaAs, its magnetic counterparts, i.e., the time-reversal breaking Weyl and nodal line Semimetals, remain elusive. They are predicted to exhibit exotic properties distinct from the inversion breaking TSMs including TaAs. In this paper, we identify the magnetic topological semimetal states in the ferromagnetic half-metal compounds Co2TiX (X = Si, Ge, or Sn) with Curie temperatures higher than 350 K. Our first-principles band structure calculations show that, in the absence of spin-orbit coupling, Co2TiX features three topological nodal lines. The inclusion of spin-orbit coupling gives rise to Weyl nodes, whose momentum space locations can be controlled as a function of the magnetization direction. Our results not only open the door for the experimental realization of topological semimetal states in magnetic materials at room temperature, but also suggest potential applications such as unusual anomalous Hall effect in engineered monolayers of the Co2TiX compounds at high temperature.
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discovery of a new type of topological weyl fermion semimetal state in moxw1 xte2
Nature Communications, 2016Co-Authors: Ilya Belopolski, Nasser Alidoust, Guang Bian, Guoqing Chang, Daniel S. Sanchez, Yukiaki Ishida, Tay Rong Chang, Hao Zheng, Xingchen Pan, Madhab NeupaneAbstract:The recent discovery of a Weyl semimetal in TaAs offers the first Weyl fermion observed in nature and dramatically broadens the classification of topological phases. However, in TaAs it has proven challenging to study the rich transport phenomena arising from emergent Weyl fermions. The series MoxW1-xTe2 are inversion-breaking, layered, tunable Semimetals already under study as a promising platform for new electronics and recently proposed to host Type II, or strongly Lorentz-violating, Weyl fermions. Here we report the discovery of a Weyl semimetal in MoxW1-xTe2 at x=25%. We use pump-probe angle-resolved photoemission spectroscopy (pump-probe ARPES) to directly observe a topological Fermi arc above the Fermi level, demonstrating a Weyl semimetal. The excellent agreement with calculation suggests that MoxW1-xTe2 is a Type II Weyl semimetal. We also find that certain Weyl points are at the Fermi level, making MoxW1-xTe2 a promising platform for transport and optics experiments on Weyl Semimetals.
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room temperature magnetic topological weyl fermion and nodal line semimetal states in half metallic heusler co2tix x si ge or sn
Scientific Reports, 2016Co-Authors: Guoqing Chang, Ilya Belopolski, Nasser Alidoust, Guang Bian, Daniel S. Sanchez, Hao Zheng, Bahadur Singh, Chuanghan Hsu, Suyang Xu, Songtian S. ZhangAbstract:Topological Semimetals (TSMs) including Weyl Semimetals and nodal-line Semimetals are expected to open the next frontier of condensed matter and materials science. Although the first inversion breaking Weyl semimetal was recently discovered in TaAs, its magnetic counterparts, i.e., the time-reversal breaking Weyl and nodal line Semimetals, remain elusive. They are predicted to exhibit exotic properties distinct from the inversion breaking TSMs including TaAs. In this paper, we identify the magnetic topological semimetal states in the ferromagnetic half-metal compounds Co2TiX (X = Si, Ge, or Sn) with Curie temperatures higher than 350 K. Our first-principles band structure calculations show that, in the absence of spin-orbit coupling, Co2TiX features three topological nodal lines. The inclusion of spin-orbit coupling gives rise to Weyl nodes, whose momentum space locations can be controlled as a function of the magnetization direction. Our results not only open the door for the experimental realization of topological semimetal states in magnetic materials at room temperature, but also suggest potential applications such as unusual anomalous Hall effect in engineered monolayers of the Co2TiX compounds at high temperature.
Nasser Alidoust - One of the best experts on this subject based on the ideXlab platform.
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magnetic and noncentrosymmetric weyl fermion Semimetals in the r alge family of compounds r rare earth
Physical Review B, 2018Co-Authors: Guoqing Chang, Ilya Belopolski, Nasser Alidoust, Guang Bian, Shinming Huang, Daniel S. Sanchez, Bahadur Singh, Chuanghan Hsu, Hao ZhengAbstract:Weyl Semimetals are novel topological conductors that host Weyl fermions as emergent quasiparticles. In this Rapid Communication, we propose a new type of Weyl semimetal state that breaks both time-reversal symmetry and inversion symmetry in the $R\mathrm{AlGe}$ ($R=\mathrm{rare}\ensuremath{-}\mathrm{earth}$) family. Compared to previous predictions of magnetic Weyl semimetal candidates, the prediction of Weyl nodes in $R\mathrm{AlGe}$ is more robust and less dependent on the details of the magnetism because the Weyl nodes are generated already by the inversion breaking and the ferromagnetism acts as a simple Zeeman coupling that shifts the Weyl nodes in $k$ space. Moreover, $R\mathrm{AlGe}$ offers remarkable tunability, which covers all varieties of Weyl Semimetals including type I, type II, inversion breaking, and time-reversal breaking, depending on a suitable choice of the rare-earth elements. Furthermore, the unique noncentrosymmetric and ferromagnetic Weyl semimetal state in $R\mathrm{AlGe}$ enables the generation of spin currents.
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room temperature magnetic topological weyl fermion and nodal line semimetal states in half metallic heusler co 2 tix x si ge or sn
Scientific Reports, 2016Co-Authors: Guoqing Chang, Ilya Belopolski, Nasser Alidoust, Guang Bian, Daniel S. Sanchez, Songtian S. Zhang, Hao Zheng, Bahadur Singh, Chuanghan Hsu, Hsin LinAbstract:Topological Semimetals (TSMs) including Weyl Semimetals and nodal-line Semimetals are expected to open the next frontier of condensed matter and materials science. Although the first inversion breaking Weyl semimetal was recently discovered in TaAs, its magnetic counterparts, i.e., the time-reversal breaking Weyl and nodal line Semimetals, remain elusive. They are predicted to exhibit exotic properties distinct from the inversion breaking TSMs including TaAs. In this paper, we identify the magnetic topological semimetal states in the ferromagnetic half-metal compounds Co2TiX (X = Si, Ge, or Sn) with Curie temperatures higher than 350 K. Our first-principles band structure calculations show that, in the absence of spin-orbit coupling, Co2TiX features three topological nodal lines. The inclusion of spin-orbit coupling gives rise to Weyl nodes, whose momentum space locations can be controlled as a function of the magnetization direction. Our results not only open the door for the experimental realization of topological semimetal states in magnetic materials at room temperature, but also suggest potential applications such as unusual anomalous Hall effect in engineered monolayers of the Co2TiX compounds at high temperature.
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discovery of a new type of topological weyl fermion semimetal state in moxw1 xte2
Nature Communications, 2016Co-Authors: Ilya Belopolski, Nasser Alidoust, Guang Bian, Guoqing Chang, Daniel S. Sanchez, Yukiaki Ishida, Tay Rong Chang, Hao Zheng, Xingchen Pan, Madhab NeupaneAbstract:The recent discovery of a Weyl semimetal in TaAs offers the first Weyl fermion observed in nature and dramatically broadens the classification of topological phases. However, in TaAs it has proven challenging to study the rich transport phenomena arising from emergent Weyl fermions. The series MoxW1-xTe2 are inversion-breaking, layered, tunable Semimetals already under study as a promising platform for new electronics and recently proposed to host Type II, or strongly Lorentz-violating, Weyl fermions. Here we report the discovery of a Weyl semimetal in MoxW1-xTe2 at x=25%. We use pump-probe angle-resolved photoemission spectroscopy (pump-probe ARPES) to directly observe a topological Fermi arc above the Fermi level, demonstrating a Weyl semimetal. The excellent agreement with calculation suggests that MoxW1-xTe2 is a Type II Weyl semimetal. We also find that certain Weyl points are at the Fermi level, making MoxW1-xTe2 a promising platform for transport and optics experiments on Weyl Semimetals.
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room temperature magnetic topological weyl fermion and nodal line semimetal states in half metallic heusler co2tix x si ge or sn
Scientific Reports, 2016Co-Authors: Guoqing Chang, Ilya Belopolski, Nasser Alidoust, Guang Bian, Daniel S. Sanchez, Hao Zheng, Bahadur Singh, Chuanghan Hsu, Suyang Xu, Songtian S. ZhangAbstract:Topological Semimetals (TSMs) including Weyl Semimetals and nodal-line Semimetals are expected to open the next frontier of condensed matter and materials science. Although the first inversion breaking Weyl semimetal was recently discovered in TaAs, its magnetic counterparts, i.e., the time-reversal breaking Weyl and nodal line Semimetals, remain elusive. They are predicted to exhibit exotic properties distinct from the inversion breaking TSMs including TaAs. In this paper, we identify the magnetic topological semimetal states in the ferromagnetic half-metal compounds Co2TiX (X = Si, Ge, or Sn) with Curie temperatures higher than 350 K. Our first-principles band structure calculations show that, in the absence of spin-orbit coupling, Co2TiX features three topological nodal lines. The inclusion of spin-orbit coupling gives rise to Weyl nodes, whose momentum space locations can be controlled as a function of the magnetization direction. Our results not only open the door for the experimental realization of topological semimetal states in magnetic materials at room temperature, but also suggest potential applications such as unusual anomalous Hall effect in engineered monolayers of the Co2TiX compounds at high temperature.
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fermi surface interconnectivity and topology in weyl fermion Semimetals taas tap nbas and nbp
Physical Review B, 2015Co-Authors: Chicheng Lee, Ilya Belopolski, Nasser Alidoust, Madhab Neupane, Guang Bian, Guoqing Chang, Shinming Huang, Daniel S. Sanchez, Hao ZhengAbstract:The family of binary compounds including TaAs, TaP, NbAs, and NbP was recently discovered as the first realization of Weyl Semimetals. In order to develop a comprehensive description of the charge carriers in these Weyl Semimetals, we performed detailed and systematic electronic band structure calculations which reveal the nature of Fermi surfaces and their complex interconnectivity in TaAs, TaP, NbAs, and NbP. Our work reports a comparative and comprehensive study of Fermi surface topology and band structure details of all known members of the Weyl semimetal family and hence provides the fundamental knowledge for realizing the many predicted exotic topological quantum physics of Weyl Semimetals based on the TaAs class of materials.
