Résumé :

When twisted to angles near 1 degre, graphene multilayers provide a new window on electron correlation physics by hosting gate-tuneable strongly-correlated states, including insulators, superconductors, and unusual magnets. I will report the discovery of a new member of the family(1), a correlated electron-hole state, in double bilayer graphene (2,3). This state can be viewed as a density wave state and is intimately linked to equilibrium exciton condensation and superfluidity. The correlated states in moiré materials can be tuned without introducing chemical dopants, thus opening the door to a new class of devices. I will show the successful realization of an exemplary device, a gate-defined Josephson Junction in magic angle twisted bilayer graphene (4). By using multilayer gate technology we define the superconducting and insulating regions of a Josephson junction (JJ) in a single-crystal and observe tunable DC and AC Josephson. This work is an initial step towards devices where gate-defined correlated states are connected in single-crystal nanostructures with applications in superconducting electronics and quantum information technology.

(1) P.Rickhaus, F. K. De Vries, E. Portolés, G. Zheng, T. Taniguchi, K. Wantanabe, A. H. Macdonald, T. Ihn, and K. Ensslin, ArXiv:2005.05373 (2020).

(2) F. K. de Vries, J. Zhu, E. Portolés, G. Zheng, M. Masseroni, A. Kurzmann, T. Taniguchi, K. Watanabe, A. H. MacDonald, K. Ensslin, T. Ihn, and P. Rickhaus, PRL 125 (17)

(3) P. Rickhaus, G. Zheng, J. L. Lado, Y. Lee, A. Kurzmann, M. Eich, R. Pisoni, C. Tong, R. Garreis, C. Gold, M. Masseroni, T. Taniguchi, K. Wantanabe, T. Ihn, and K. Ensslin, Nano Lett. 19, 8821 (2019).

(4) F. K. de Vries, E. Portolés, G. Zheng, T. Taniguchi, K. Wantanabe, T. Ihn, K. Ensslin, and P. Rickhaus, arXiv:2011.00011, accepted in Nat. Nano

Contact : equipe-seminaires-nano@listes.grenoble.cnrs.fr