Even empty gaps have a colour. Now scientists have shown that quantum jumps of electrons can change the colour of gaps between nano-sized balls of gold. The new results, published in the journal Nature, set a fundamental quantum limit on how tightly light can be trapped.
The team from the Universities of Cambridge, the Basque Country and Paris have combined tour de force experiments with advanced theories to show how light interacts with matter at nanometre sizes. The work shows how they can literally see quantum mechanics in action in air at room temperature.
Because electrons in a metal move easily, shining light onto a tiny crack pushes electric charges onto and off each crack face in turn, at optical frequencies. The oscillating charge across the gap produces a ‘plasmonic’ colour for the ghostly region in-between, but only when the gap is small enough.
Team leader Professor Jeremy Baumberg from the University of Cambridge Cavendish Laboratory suggests we think of this like the tension building between a flirtatious couple staring into each other’s eyes. As their faces get closer the tension mounts, and only a kiss discharges this energy.
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Image: Nano-sized balls of gold
Image credit: M Hawkeye, NanoPhotonics, Cambridge
Reproduced courtesy of the University of Cambridge
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Quantum kisses change the colour of nothing
8 November 2012
New insights from research suggest ways to measure the world at the scale of single atoms and molecules.