MPL DLS Talk: Bilayer graphene: rich in physics and good for devices

Speaker: Prof. Klaus Ensslin, Professor of Physics at ETH Zürich, President of the Swiss Quantum Commission

Abstract
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.

Biography
Education
May 83 Vordiplom (Bachelors), University of Munich, Germany
April 86 Diploma in physics (Masters), Eidgenössische Technische Hochschule, ETH-Zürich, Switzerland
January 89 Ph. D. in physics at Max-Planck Institute for solid state research, Stuttgart, Germany
January 1995 Habilitation and Privatdozent at the Physics Department of the University of Munich, Germany

Employment
June 86 - Feb. 89 Ph. D. student at Max-Planck-Institut for solid state research, Stuttgart, Germany
March 89 - March 91 Postdoc at the University of California in Santa Barbara
April 91 - Sept. 95 University Assistant at the Physics Department of the University of Munich, Germany
since October 1995 Professor of Physics at ETH Zurich, Switzerland
2011 - 2022 Director of National Center for Competence in Research on Quantum Science and Technology
Since January 2026 President of the Swiss Quantum Commission

Zoom Link
https://eu02web.zoom-x.de/j/61245265377?pwd=xD5pyjvV6B80H2siVXoptd6juhH0Ez.1

Meeting-ID: 612 4526 5377
Kenncode: 431516
Further Information: https://mpl.mpg.de/de/events/termin/klaus-ensslin-bilayer-graphene-rich-in-physics-and-good-for-devices