Rout Prasanna, Papadopoulos Nikos, Peñaranda Fernando, Watanabe Kenji, Taniguchi Takashi, Prada Elsa, San-Jose Pablo, Goswami Srijit
QuTech and Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA, Delft, The Netherlands.
Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC. Sor Juana Inés de la Cruz 3, 28049, Madrid, Spain.
Nat Commun. 2024 Jan 29;15(1):856. doi: 10.1038/s41467-024-44952-6.
Bilayer graphene encapsulated in tungsten diselenide can host a weak topological phase with pairs of helical edge states. The electrical tunability of this phase makes it an ideal platform to investigate unique topological effects at zero magnetic field, such as topological superconductivity. Here we couple the helical edges of such a heterostructure to a superconductor. The inversion of the bulk gap accompanied by helical states near zero displacement field leads to the suppression of the critical current in a Josephson geometry. Using superconducting quantum interferometry we observe an even-odd effect in the Fraunhofer interference pattern within the inverted gap phase. We show theoretically that this effect is a direct consequence of the emergence of helical modes that connect the two edges of the sample. The absence of such an effect at high displacement field, as well as in bare bilayer graphene junctions, supports this interpretation and demonstrates the topological nature of the inverted gap.
包裹在二硒化钨中的双层石墨烯可以承载具有成对螺旋边缘态的弱拓扑相。该相的电学可调性使其成为研究零磁场下独特拓扑效应（如拓扑超导）的理想平台。在此，我们将这种异质结构的螺旋边缘与超导体耦合。在零位移场附近，体态能隙的反转伴随着螺旋态，导致约瑟夫森几何结构中临界电流的抑制。利用超导量子干涉测量，我们在反转能隙相的夫琅禾费干涉图样中观察到奇偶效应。我们从理论上表明，这种效应是连接样品两条边缘的螺旋模式出现的直接结果。在高位移场以及裸双层石墨烯结中不存在这种效应，支持了这一解释，并证明了反转能隙的拓扑性质。
