Friday, November 22, 2013

Nano-size superfluidity

Scientists at EPFL have provided the first experimental evidence of superfluidity at the nanoscale, shedding light on the fundamental basis of the phenomenon.

Superfluidity refers to a state in which matter behaves like a liquid with zero viscosity. Much like superconductivity, this phenomenon occurs at extremely low temperatures and can cause a liquid like helium to behave in the strangest ways, e.g. roll up out of a container or even create a perpetual fountain. But beyond just a fascinating curiosity, superfluidity is frequently used in high-precision applications like quantum gyroscopes and even satellites that measure infrared radiation in space. With a few exceptions, superfluidity has generally been regarded as a macroscopic phenomenon, resulting from ‘bulky’ collections of particles rather than individual atoms. But in a recent Physical Review Letters paper, EPFL researchers have now shown that, at least in liquids, superfluidity involves dynamics that go down to the nanoscale.The most common superfluid element is helium-4, which is used in both research and applications like cooling down the Large Hadron Collider at CERN. With the exception of Bose-Einstein condensates – a state of matter that occurs at extremely low temperatures where particles reach their lowest energy – superfluidity has been thus far considered to be macroscopic. Consequently, helium-4 is usually employed in bulk in relevant studies, which do not take into account the contributions of individual atoms to the overall phenomenon.

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