In a discovery that brings a legendary quantum theory to life, physicists at Princeton University have directly observed Hofstadter’s butterfly — a fractal pattern in electron energy levels that was first predicted in 1976 but had never before been seen in a real material.
The breakthrough, which occurred during an experiment on graphene superconductivity, offers a rare look at a self-repeating quantum energy spectrum and opens the door to new insights in fundamental physics.
According to the research team of the study published in Nature, was not searching for Hofstadter’s butterfly when they stumbled upon it. Their goal was to investigate how electrons behave in twisted bilayer graphene, a form of carbon that becomes superconductive under certain conditions.
An unexpected twist in their experimental setup changed everything. A slight misalignment during the sample preparation created the ideal geometry to reveal the elusive fractal pattern. Under a magnetic field, the material displayed an intricate, repeating energy structure — just like the one physicist Douglas Hofstadter described nearly fifty years ago.
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