Novel interference state by tuning gate in magic-angle twisted bilayer graphene
Lian Wen1,2*, Kuo-En Chang1,2, Chiu-Hau Huang1,2, Ching-Hua Kao1,2, Yu-Chiang Hsieh1,2, Shin-Ji Fung1,2, Jun-Sheng Wu1,2, Shih-Hsiang Chao1,2, Tse-Ming Chen1,2
1Department of Physics, National Cheng Kung University, Tainan, Taiwan
2Center for Quantum Frontier of Research and Technology, National Cheng Kung University, Tainan, Taiwan
* Presenter:Lian Wen,
Magic-angle twisted bilayer graphene (MATBG) has recently emerged as a versatile platform that combines metallic, superconducting, magnetic and insulating phases in a single crystal¹. One of the applications by tuning the correlated states in MATBG is the development of Josephson junction (JJ)². It was confirmed that the critical current in JJ can be modified by adjusting the gate of the barrier². As a result, we fabricate MATBG-based superconducting quantum interference device (SQUID) using bubble free transfer technique³, e-beam lithography and conduct electrical measurements. Furthermore, this SQUID can become an asymmetry loop by unmatched critical current with different gate between two JJs⁴. With this advantage, we plan to tune the SQUID into asymmetry and improve its sensitivity under specific magnetic field region⁴. This provides the opportunity for future applications in superconducting electronics⁵ and quantum information technology⁶.

1. Cao, Y. et al. Unconventional superconductivity in magic-angle graphene superlattices. Nature. 556, 43–50 (2018)
2. de Vries, F. K. Gate-defined Josephson junctions in magic-angle twisted bilayer graphene. Nature Nanotechnology. 16, 760-763(2021)
3. D. G. Purdie. Cleaning interfaces in layered materials heterostructures. Nature Communications volume 9, Article number: 5387 (2018)
4. J. Clarke and A. I. Braginski. The SQUID Handbook (Wiley, 2004), Vol. 1.
5. Tinkham, M. Introduction to Superconductivity (Courier, 2004), vol 2.
6. Wendin, G. Quantum information processing with superconducting circuits: a review. Rep. Progr. Phys. 80, 106001 (2017).

Keywords: SQUID, superconductor, Josephson junction, graphene