Higgs mode in superconductors studied by intense terahertz pulse technique

2018 Fiscal Year Final Research Report

• Project/Area Number: 15H05452
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Single-year Grants
• Research Field: Condensed matter physics I
• Research Institution: The University of Tokyo
• Principal Investigator: MATSUNAGA RYUSUKE 東京大学, 物性研究所, 准教授 (50615309)
• Project Period (FY): 2015-04-01 – 2019-03-31
• Keywords: 光物性 / テラヘルツ / 超伝導 / ヒッグス機構

Outline of Final Research Achievements

We have investigated the collective excitation mode of order parameter amplitude associated with spontaneous symmetry breaking in superconductor, namely the Higgs mode, by using the state-of-the-art technology of intense terahertz pulse generation. We clarified the dominant contribution of the Higgs mode on nonlinear terahertz response in s-wave superconductor, indicating that the contribution of the Higgs mode is significantly underestimated in the BCS mean-field approximation. Infrared activation of the Higgs mode under strong supercurrent was also observed experimentally. We also succeeded the observation of the Higgs mode in a d-wave superconductor cuprate for the first time and investigated nonequilibrium dynamics of c-axis Josephson plasma resonance in cuprates.

Free Research Field

光物性

Academic Significance and Societal Importance of the Research Achievements

超伝導は素粒子物理と極めて高い類似性を持つことが古くから知られ、その研究の発展は物理学全体に大きな影響を及ぼしてきたが、ヒッグス粒子に相当する集団的振る舞い（ヒッグスモード）は、普遍的現象であるにも関わらずこれまでほとんど調べられていなかった。高強度テラヘルツパルスによる最先端光学測定を用いた我々の研究によって、超伝導ヒッグスモードを観測する実験が実現し、様々な超伝導体においてその性質が明らかになった。