Superconductivity is capable of increasing radiation pressure a million times stronger than normal, according to a new discovery.
Radiation pressure is the normally gentle push of electromagnetic radiation on matter, similar to the slight press light makes on a mirror. This effect is negligible in our everyday experience, on the macroscopic scale at which we live. However, this force can become significant in space, when produced by objects as powerful as stars.
The radiation pressure falling on a typical chair from a 100-watt incandescent light bulb is roughly one-trillionth as strong as atmospheric pressure at sea level. This same effect in space also drives tails of comets to always point away from the sun. This pressure can also be utilized in solar sails to propel mechanical craft through space like ships on the water. Massive laser pulses can be controlled using the radiation pressure from an oscillator within a common wristwatch.
"Radiation pressure physics in these systems have become measurable only when the oscillator is hit by millions of photons," Jani Tuorila, a theoretical physicist from the University of Oulu, said.
This new experiment explored some of the strangest effects of the bizarre world of quantum mechanics. Superconductors are best known for their ability to "levitate" under the right conditions, seemingly defying gravity.
"In the measurements, we exploited the Josephson coupling of the superconducting junctions, especially its nonlinear character," Juha Pirkkalainen from Aalto University said.
This effect takes place between a pair of superconducting materials separated by a "weak link" such as an insulator or nonconducting metal.
Researchers examined what happened when a tiny island of superconductive material was placed between the electromagnetic field and the oscillator. They found this setup increased radiation pressure by as much as a million times its normal strength. This greatly amplified signal made it possible for the oscillator to distinguish detail in the electromagnetic field down to the level of single photon — the smallest "piece" of light. The field, in turn, responded to the device at the level of a single phonon — the quantum "step" of oscillation.
This study could lead to the observation of quantum effects taking place in large bodies in ways never before seen by physicists. Some researchers believe quantum effects only take place on extremely small scales, but there is little mathematical reasoning behind this idea.
Future research could use techniques of this study to examine the effect of radiation pressure on single photons of light.
Analysis of the amplification of radiation pressure through the use of a superconducting island was published in the journal Nature Communications.
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