Various ordered states of high temperature superconductors studied by high resolution laser-based angle-resolved photoelectron spectroscopy

2018 Fiscal Year Final Research Report

• Project/Area Number: 16H06013
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Single-year Grants
• Research Field: Condensed matter physics II
• Research Institution: The University of Tokyo
• Principal Investigator: Kondo Takeshi 東京大学, 物性研究所, 准教授 (40613310)
• Project Period (FY): 2016-04-01 – 2018-03-31
• Keywords: 光電子分光 / 超伝導 / レーザー

Outline of Final Research Achievements

The energy gap developed from the high temperature above the superconducting transition temperature is measured by ultra-precision photoelectron spectroscopy realized by using a laser as a light source. In particular, we focused on Bi2Sr2Ca2Cu3O10 + δ (Bi2223) with three superconducting layers (CuO2 planes) per unit cell. A new phenomenon of superconductors in optimally doped Bi2223 is revealed. Hybridization of Bogoliubov bands derived from inner and outer CuO 2 planes with different energy gaps was observed, showing the splitting of the coherent peak and the associated increase of the spectral gap. Significant modulation of electron pairing has been proposed as a factor to achieve the highest critical temperature in trilayer copper oxides.

Free Research Field

電子物性

Academic Significance and Societal Importance of the Research Achievements

液体窒素温度を超える高い臨界温度を示す超伝導体が約30年前銅酸化物において発見れて以来、銅酸化物高温超伝導体は物性研究の対象として長らく主役を担ってきた。それにも関わらず、その高い超伝導臨界温度が生み出される機構に関しては未だ統一した見解が得られていない。 超伝導は、伝導を支配する電子が多数の対を組むことで安定化し、背景にある格子振動や不純物による散乱を受けることなく電流を流す特異な電子状態である。超伝導の発現機構を解明する上で、電子同士を対として結びつける”のり”を同定することが重要であり、Bi2223のレーザーARPES研究で見出した転移温度上の理解により応用研究への波及が期待される。