Article on scientist’s work where they are able to observe a negative image of a butterfly form which appears in certain energy states in materials.
“The existence of gaps changes the way electrons move through a material. Copper for example, has no gaps, whereas an insulator, like glass, has very large gaps. The relationship between energy and how dense the electrons are in a material – energy density – determines all electrical properties.”
“What you see in a Hofstadter spectrum is a very complicated structure of gaps arranged in a fractal pattern.”
“The team produced the effect by sandwiching together flat sheets of graphene – a single-atom-thickness of carbon – and another material, called boron nitride, and twisting them against each other to create what is called a superlattice.
“Graphene has hexagonal chicken wire structure and boron nitride does too. It is as if you take screen door material and put one sheet on top of other. As you rotate it you see a periodic pattern appear. You get an interference effect – a ‘moiré’ pattern. In the case of the chicken-wire structure of graphene and boron nitride, the pattern forms a fractal butterfly of energy states.”
Leave a Reply