Fabrication of graphene/graphene-nanoribbon superconductors

2019 Fiscal Year Final Research Report

• Project/Area Number: 18K18986
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 28:Nano/micro science and related fields
• Research Institution: Tohoku University
• Principal Investigator: Katsuaki Sugawara 東北大学, 理学研究科, 准教授 (70547306)
• Project Period (FY): 2018-06-29 – 2020-03-31
• Keywords: グラフェン / グラフェンナノリボン / 超伝導 / ARPES

Outline of Final Research Achievements

To realize monolayer graphene and graphene-nanoribbon superconductors and the mechanism of superconducting transition, I have fabricated a alkali-metal-coated monolayer graphene and graphene nanoribbon by molecular-beam epitaxy and performed high-resolution angle-resolved photoemission spectroscopy (ARPES). After depositing a potassium atom onto a monolayer graphene substrate, we found not only a folded Dirac-electron state due to a periodic potential of 2x2 superstructure but also a novel free-electron like two-dimensional electron gas. It has been well known that the free-electron like state plays an important rule for a superconductivity in graphite intercalation compounds (GICs). Surprisingly, I found that the folded Dirac-electron state and free-electron like state may be hybridized near the Fermi levels. These results suggests that the superconductivity in the metal coated graphene materials is induced by hybridization between Dirac electron and free-electron like state.

Free Research Field

グラフェン

Academic Significance and Societal Importance of the Research Achievements

これまで世界中の研究者誰もが原子層グラフェンの超伝導化が実現出来なかった背景を考慮すると、本研究によって、ディラック電子状態のみならず自由電子的２次元電子ガスの両方が必要であるという研究結果を得られたことは、今後グラフェンにおける新たな新規物性を誘起する上で重要な成果と考えていえる。
グラフェンやグラフェンナノリボンは「強固、軽量、高熱伝導、フレキシブル、透明、高電気伝導」と様々な機能性を有しているが、それらの一つ高電気伝導性を超伝導に置き換えることができれば、量子コンピューターなどの産業応用に多大な影響を与えるだけでなく、今後のグラフェン超伝導の研究が世界的に拡がることが期待できる。