Experimental observation and development of the novel quantum phenomena originating from the Dirac/Weyl fermions in the bulk materials

2018 Fiscal Year Final Research Report

• Project/Area Number: 16H06114
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Single-year Grants
• Research Field: Physical properties of metals/Metal-base materials
• Research Institution: Osaka University
• Principal Investigator: Murakawa Hiroshi 大阪大学, 理学研究科, 助教 (40611744)
• Project Period (FY): 2016-04-01 – 2018-03-31
• Keywords: ワイル半金属 / トポロジカル物性 / ランダウ準位 / 磁気抵抗効果

Outline of Final Research Achievements

We have investigated for the novel phenomena originating from the Weyl fermion in the crystals. We synthesized the large size of the single crystals of the Weyl semimetal TaAs and NbAs and measured their electrical conducting properties under the precise control of the magnetic-field directions. We observed the negative magnetoresistance stemming from the nondissipative conduction of the Weyl fermions and the unusual plateau in the Hall resistivity in the quantum limit. Furthermore, we found that the Landau levels in the system including a pair of the Weyl points changes discontinuously just by changing the magnetic-field direction as if the band topology changed. This result implies the new energy quantization rule in the Weyl fermion, which cannot be explained by the conventional theories.
We synthesized the extremely high quality single crystal of NbAs2 and observed the magnetoresistance of 2 million, which is two orders higher than the other reported binary semimetals.

Free Research Field

物性物理学実験

Academic Significance and Societal Importance of the Research Achievements

本研究では、ワイル半金属の大型の良質単結晶を用いて低温強磁場中での物性測定を行い、
結晶中の相対論的粒子の基本的な性質や、特殊なバンド構造に由来した新奇な量子現象について、これまでの理論的な提案を実証するのみならず、従来の常識では説明できない新たな発見をすることができた。シンプルな系を用いて電子系のトポロジーを反映した本質的な現象を実験的に明らかにした本研究成果は、これからの物性物理学の進展に大きく貢献するものである。