All previously known oscillations in a magnetic field require low-temperatures, typically equal to when helium becomes a liquid. In contrast, the new oscillations were observed at very high temperatures, well above room temperature.
Professor Sir Andre Geim from The University of Manchester, who won the Nobel Prize for Physics in 2010 for his work on graphene, led the experimental effort and said: “Oscillatory quantum effects always present milestones in our understanding of materials properties. They are exceedingly rare. It is more than 30 years since a new type of quantum oscillation was reported.”
He added: “Our oscillations stand out by their extreme robustness, happening under ambient conditions in easily accessible magnetic fields.”
Another remarkable aspect of this work is that graphene superlattices have previously been used to study so-called Hofstadter butterflies, subtle changes in the electronic structure with magnetic field. These changes exhibit a fascinating fractal structure.
Professor Vladimir Falko, Director of the National Graphene Institute who provided theoretical support in this work commented: “Our work helps to demystify the Hofstadter butterfly. The complex fractal structure of the Hofstadter butterfly spectrum can be understood as simple Landau quantisation in the sequence of new metals created by magnetic field.”