Theoretical proposal for novel devices based on the Kitaev model

2023 Fiscal Year Final Research Report

• Project/Area Number: 21H01025
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
• Research Institution: Tohoku University
• Principal Investigator: Tsuchiura Hiroki 東北大学, 工学研究科, 准教授 (30374961)
• Co-Investigator(Kenkyū-buntansha): 古賀 昌久 東京工業大学, 理学院, 准教授 (90335373)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: キタエフ模型 / マヨラナ準粒子 / 異常なジョセフソン効果 / 並進・回転対称性の破れた超伝導状態 / 超伝導ダイオード効果

Outline of Final Research Achievements

The objective of this research project is to propose theoretical devices with relatively simple controllability that take advantage of the novel physical properties predicted in the Kitaev model. Two types of the Kitaev model are known: a quantum spin type and a one-dimensional p-wave superconductor type. With regard to the quantum spin type model, a new switching mechanism has been proposed that controls the transport of magnetic excitations by Majorana quasiparticles. Furthermore, we predicted the emergence of rotationally symmetry-breaking superconducting states in carrier-doped systems, along with the proposal of a superconducting switch utilizing this mechanism. With regard to the 1D p-wave model, various Josephson current-phase relationships and also the superconducting diode effect have been predicted when the models are arranged in parallel pairs.

Free Research Field

物性理論

Academic Significance and Societal Importance of the Research Achievements

近年，トポロジカル絶縁体・超伝導体という概念が確立・浸透し，それに伴いこれらの物質で予想される新しい現象を活用したデバイス開発が期待されてきた．その代表的なものに，これらの物質で期待されるマヨラナ準粒子状態を用いた量子計算素子の開発がある．しかしながら，そのためにはマヨラナ準粒子同士の位置交換という極めて困難な操作を実現する必要があり，実用化には遠い．本研究課題では，マヨラナ準粒子の存在が期待されるキタエフ模型をもとにして，比較的簡便な操作性をもつ新奇デバイス構造を理論的に3種類提案したことにより，トポロジカル物質の応用に新たな活路を開くことができたと考えている．