|
セガワ コウジ
SEGAWA KOJI
瀬川 耕司 所属 京都産業大学 理学部 物理科学科 職種 教授 |
|
| 言語種別 | 英語 |
| 発行・発表の年月 | 2011/11 |
| 形態種別 | 研究論文 |
| 標題 | Unexpected mass acquisition of Dirac fermions at the quantum phase transition of a topological insulator |
| 執筆形態 | その他 |
| 掲載誌名 | NATURE PHYSICS |
| 出版社・発行元 | NATURE PUBLISHING GROUP |
| 巻・号・頁 | 7(11),pp.840-844 |
| 著者・共著者 | T. Sato,Kouji Segawa,K. Kosaka,S. Souma,K. Nakayama,K. Eto,T. Minami,Yoichi Ando,T. Takahashi |
| 概要 | The three-dimensional (3D) topological insulator is a novel quantum state of matter where an insulating bulk hosts a linearly dispersing surface state, which can be viewed as a sea of massless Dirac fermions protected by the time-reversal symmetry (TRS). Breaking the TRS by a magnetic order leads to the opening of a gap in the surface state(1), and consequently the Dirac fermions become massive. It has been proposed theoretically that such a mass acquisition is necessary to realize novel topological phenomena(2,3), but achieving a sufficiently large mass is an experimental challenge. Here we report an unexpected discovery that the surface Dirac fermions in a solid-solution system TlBi(S1-xSex)(2) acquire a mass without explicitly breaking the TRS. We found that this system goes through a quantum phase transition from the topological to the non-topological phase, and, by tracing the evolution of the electronic states using the angle-resolved photoemission, we observed that the massless Dirac state in TlBiSe2 switches to a massive state before it disappears in the non-topological phase. This result suggests the existence of a condensed-matter version of the 'Higgs mechanism' where particles acquire a mass through spontaneous symmetry breaking. |
| DOI | 10.1038/NPHYS2058 |
| ISSN | 1745-2473 |
| PermalinkURL | https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=80555131220&origin=inward |