4.9.2020 Superconductivity from graphene with flat bands (Peltonen)

Graphene, a two-dimensional structure of carbon atoms reminiscent of a honeycomb, is a special material. Its thermal conductivity, electrical conductivity, and strength are top class. It is because of these reasons that graphene has attracted a lot of scientific attention since its discovery in 2004. One property is missing, however: superconductivity, that is, the perfect vanishing of electrical resistance below a certain critical temperature. In his doctoral dissertation Teemu Peltonen studied theoretically how graphene can be made superconducting and how it may help us reaching room-temperature superconductivity, which would revolutionize everything from computers to electric power transmission if realized.
Published
4.9.2020

The direction of condensed matter physics changed in spring 2018 when scientists at the Massaschusetts Institute of Technology (MIT) observed that graphene becomes superconducting when another layer of graphene is added on top of it, rotated by one degree. This new material, called twisted bilayer graphene, has since been extensively studied, with the aim of trying to understand the origin of superconductivity.

Towards higher temperatures through strain

In the doctoral dissertation Teemu Peltonen introduced a theoretical model that is simple but still able to explain the results of the experiments. As promising as the results are, at the moment it seems that the critical temperature of twisted bilayer graphene cannot be made very high, yet alone room temperature. Because of this also another method was introduced in the dissertation: graphene can be made superconducting also by straining it appropriately. Based on the results it was predicted that the critical temperature could be increased much higher than what could be done in twisted bilayer graphene.

"It seems that the exact strain profile is not important, but instead it should be periodic and strong enough. In other words graphene should be stretched and squeezed consecutively", Peltonen summarizes.

Support for the doctoral dissertation has come from the Academy of Finland and from the Emil Aaltonen foundation. Computational resources have been offered by the Finnish Grid and Cloud Infrastructure (FGCI).

The doctoral dissertation has been published in the JYU Dissertations series, number 250, Ä¢¹½Ö±²¥, Jyväskylä, 2020. ISBN 978-951-39-8221-8 (PDF), URN:ISBN:978-951-39-8221-8, ISSN 2489-9003
Link to the publication: 

Teemu Peltonen graduated from the Cygnaeus High School in Jyväskylä in spring 2008 and graduated from the Ä¢¹½Ö±²¥ in summer 2015 from the Master's Degree Programme in Nanoscience majoring in theoretical physics. The supervisor of the doctoral dissertation was Professor Tero Heikkilä.

For further information:
Teemu Peltonen, teemu.j.peltonen@student.jyu.fi

M.Sc. Teemu Peltonen defends his doctoral dissertation in Theoretical Physics "Superconductivity from graphene with flat bands" on Friday 4th of September at the Ä¢¹½Ö±²¥ at 12:00 noon. Opponent Professor Jörg Schmalian (Institute for Theoretical Condensed Matter Physics, Karlsruhe Institute of Technology, Germany) and Custos Professor Tero Heikkilä (Ä¢¹½Ö±²¥). The doctoral dissertation is held in English.

The audience can follow the dissertation online.
Link to the Zoom Webinar (Zoom application or Google Chrome web browser recommended):