Investigation of quantum dynamics of vortices and quantum critical phenomena in highly crystalline 2D superconductors

2023 Fiscal Year Final Research Report

• Project/Area Number: 21H01792
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 29010:Applied physical properties-related
• Research Institution: Tohoku University
• Principal Investigator: Nojima Tsutomu 東北大学, 金属材料研究所, 准教授 (80222199)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 超伝導 / 2次元超伝導 / 量子磁束 / 電気二重層トランジスタ

Outline of Final Research Achievements

We studied the quantum vortex states and their dynamics in highly crystalline two-dimensional (2D) superconductors by using the electric-field-induced 2D electron system at the surface of MoS2 single crystals and the exfoliated NbSe2 single crystal films. By measuring the transport properties of them as a function of temperature, magnetic field, electrical current and thickness in detail, we successfully made the comprehensive vortex phase diagrams of 2D superconductors containing the quantum fluctuation. Through the comparison of the　obtained results, we clarified the origine of the quantum metallic state, where the drop in temperature dependence of resistance levels off at low temperature in out-of-plane magnetic field, the current induced quantum vortex-antivortex state at zero field, and their dynamical phase transitions, all of which were suggested to be typical of 2D superconductors.

Free Research Field

低温物理学

Academic Significance and Societal Importance of the Research Achievements

物質が持つ次元性を3次元から2次元へ下げることにより、量子ゆらぎの効果が飛躍的に大きくなることはスピン系をはじめ様々な物質系で共通して期待される事象である。本研究成果は、これを巨視的な超伝導の磁束系やそのダイナミクスにおいて明らかにしたものであり広い学術分野にわたる波及効果を持つ。本研究で得られた量子金属状態や磁束-反磁束状態の動的転移といった2次元超伝導体の磁束ダイナミクスは、磁束状態に対する深い知見が不可欠な超伝導線材応用だけでなく、超伝導量子ビット等といった薄膜デバイスを用いたエレクトロニクス応用へ向けた基礎研究となるため、社会的意義も十分に有する。