CoQuS-Talk by Pertti Hakonen; Aalto University, Finland

16.10.2017 17:30 - 18:30

on "Fractional quantum Hall effect and Wigner crystallization in suspended graphene"

The structure of the many-body ground state of a 2D electron gas has been under intense theoretical and experimental investigation over the past 40 years. Many unexpected findings, e.g. such as the fractional quantum Hall effect, have made this research area as one of the most fascinating of modern condensed matter physics. As for the present aspirations, fractional elementary excitations and their possible non-Abelian statistics have raised hopes for unconventional applications of these systems in future quantum technologies.

Suspended monolayer graphene forms and excellent, new platform to investigate these many-body phenomena. Suspended graphene provides a system where the Coulomb energy is maximized owing to the small dielectric contstant of its environment, much lower than obtained in the regular semiconductor heterostructures. This favors crystallization of the electrons into a Wigner crystal phase as well as it enhances the energy gaps of the incompressible fractional quantum Hall (FQH) liquid states. Hence, an unprecedentedly rich sequence of ordered phases can be expected.

We have investigated the Wigner crystal order and the FQHliquid phases of suspended graphene in Corbino geometry. Our results indicate an unconventional sequence of FQH phases, which is consistent with the composite fermion theory including weak residual interactions. With lowering electron density, the sequence of FQH states is interrupted by Wigner crystal order at Landau level filling factors ν∼1/7-1/5. In my talk, besides the basic 2D electron gas many-body correlations, I will discuss the basic experimental results giving rise to the above conclusions.

 

Monday, 16 October  2017,
16:30 get-together with coffe and snacks!

 

University of Vienna, Boltzmanngasse 5, Lise-Meitner-Hörsaal

The seminar talk will be preceded by a CoQus Student talk at 17:00
by

Armin Hochrainer

University of Vienna

Measuring the momentum correlation between two light beams by detecting one

 

Hosted by: Anton Zeilinger