期刊
PHYSICAL REVIEW MATERIALS
卷 3, 期 7, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevMaterials.3.071201
关键词
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资金
- Shenzhen Peacock Plan [KQTD2016053112042971]
- Science and Technology Planning Project of Guangdong Province [2016B050501005]
- US Department of Energy (DOE), Office of Science, Basic Energy Sciences [DE-FG02-07ER46352]
- National Energy Research Scientific Computing Center through DOE [DE-AC02-05CH11231]
- Ministry of Science and Technology (MOST) in Taiwan [105-2112-M-110-014-MY3]
- Young Scholar Fellowship Program by Ministry of Science and Technology (MOST) in Taiwan, under MOST Grant for the Columbus Program [MOST 108-2636-M-006-002]
- National Cheng Kung University, National Center for Theoretical Sciences (NCTS)
- Higher Education Sprout Project, Ministry of Education
- MOST, Taiwan [MOST 107-2627-E-006-001]
- Academia Sinica, Taiwan [AS-iMATE-107-11]
Materials with triply degenerate nodal points in their low-energy electronic spectrum produce crystallinesymmetry-enforced threefold fermions, which conceptually lie between the twofold Weyl and fourfold Dirac fermions. Here, we show how a silver-based Dirac semimetal BaAgAs realizes threefold fermions through our first-principles calculations combined with a low-energy effective k . p model Hamiltonian analysis. BaAgAs is shown to harbor triply degenerate nodal points, which lie on its C-3 rotation axis, and are protected by the C-6v (C-2 circle times C-3v) point-group symmetry in the absence of spin-orbit coupling (SOC) effects. When the SOC is turned on, BaAgAs transitions into a nearly ideal Dirac semimetal state with a pair of Dirac nodes lying on the C-3 rotation axis. We show that breaking inversion symmetry in the BaAgAs1-xPx alloy yields a clean and tunable threefold fermion semimetal. Systematic relaxation of other symmetries in BaAgAs generates a series of other topological phases. BaAgAs materials thus provide another platform for exploring tunable topological properties associated with a variety of different fermionic excitations.
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