title: Continuous and reversible tuning of the disorder-driven superconductor-insulator transition in bilayer graphene.
abstract: The influence of static disorder on a quantum phase transition (QPT) is a fundamental issue in condensed matter physics. As a prototypical example of a disorder-tuned QPT, the superconductor-insulator transition (SIT) has been investigated intensively over the past three decades, but as yet without a general consensus on its nature. A key element is good control of disorder. Here, we present an experimental study of the SIT based on precise in-situ tuning of disorder in dual-gated bilayer graphene proximity-coupled to two superconducting electrodes through electrical and reversible control of the band gap and the charge carrier density. In the presence of a static disorder potential, Andreev-paired carriers formed close to the Fermi level in bilayer graphene constitute a randomly distributed network of proximity-induced superconducting puddles. The landscape of the network was easily tuned by electrical gating to induce percolative clusters at the onset of superconductivity. This is evidenced by scaling behavior consistent with the classical percolation in transport measurements. At lower temperatures, the solely electrical tuning of the disorder-induced landscape enables us to observe, for the first time, a crossover from classical to quantum percolation in a single device, which elucidates how thermal dephasing engages in separating the two regimes.
authors: Department of Physics, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea.
authors: Gil-Ho
authors: GH
authors: Lee
authors: Department of Physics, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea.
authors: Dongchan
authors: D
authors: Jeong
authors: Department of Physics, Sungkyunkwan University, Suwon 440-746, Republic of Korea.
authors: Kee-Su
authors: KS
authors: Park
authors: Department of Physics, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel.
authors: Yigal
authors: Y
authors: Meir
authors: Department of Applied Physics, Hanyang University, Ansan 426-791, Republic of Korea.
authors: Min-Chul
authors: MC
authors: Cha
authors: Department of Physics, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea.
authors: Hu-Jong
authors: HJ
authors: Lee