Park Geon-Hyoung, Lee Wonjun, Park Sein, Watanabe Kenji, Taniguchi Takashi, Cho Gil Young, Lee Gil-Ho
Deparment of Physics, Pohang University of Science and Technology, Pohang, Republic of Korea.
Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science, Pohang, Republic of Korea.
Phys Rev Lett. 2024 May 31;132(22):226301. doi: 10.1103/PhysRevLett.132.226301.
We demonstrate that the mode number of Andreev bound states in bilayer graphene Josephson junctions can be modulated by controlling the superconducting coherence length in situ. By exploiting the quadratic band dispersion of bilayer graphene, we control the Fermi velocity and thus the coherence length via the application of electrostatic gating. Tunneling spectroscopy of the Andreev bound states reveals a crossover from short to long Josephson junction regimes as we approach the charge neutral point of the bilayer graphene. Furthermore, analysis of different mode numbers of the Andreev energy spectrum allows us to estimate the phase-dependent Josephson current quantitatively. Our Letter provides a new way for studying multimode Andreev levels by tuning the Fermi velocity.
我们证明，通过原位控制超导相干长度，可以调节双层石墨烯约瑟夫森结中安德列夫束缚态的模式数。利用双层石墨烯的二次能带色散，我们通过施加静电栅极来控制费米速度，进而控制相干长度。对安德列夫束缚态的隧穿光谱研究表明，当我们接近双层石墨烯的电荷中性点时，会出现从短约瑟夫森结区到长约瑟夫森结区的转变。此外，对安德列夫能谱不同模式数的分析使我们能够定量估计与相位相关的约瑟夫森电流。我们的论文为通过调节费米速度来研究多模安德列夫能级提供了一种新方法。
