Bilayer graphene : rich in physics and good for devices

Résumé :

Electrons have a charge and a spin degree of freedom. The primitive unit cell in graphene honeycomb lattice has 2 atoms. As a consequence, there is an additional valley degree of freedom in graphene that can be tuned by gate voltages. For electrostatically-defined quantum dots in bilayer graphene this leads to a particular filling sequence, with the first 4 electrons in the s-shell and the next 8 electrons in the p-shell. The details of the level spectrum reveals many surprises, such as a singly-degenerate spin-triplet/valley-singlet states for the two carrier state. When building a qubit, one can utilize all available degrees of freedom: charge, spin and valley. For the so-called Kramers qubits, where spin and valley need to be flipped for relaxation from the excited to the ground state, lifetimes as long as 100 s have been experimentally observed. For graphene layer twisted at the magic angle one can fabricate superconducting devices such as Josephson junctions, SQUIDs and Cooper pairs boxes. In this talk I will present the prospects that graphene offers to investigate physics questions related to topology, superconductivity, spin-orbit interactions and spin-valley coupling as well as device concepts with unprecedented tuning opportunities.

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