A new type of quasiparticle – dubbed the "leviton" – has been seen by physicists in France and Switzerland. First predicted in 1996 by a team led by Leonid Levitov, the phenomenon involves the excitation of as few as one electron to create a wave that propagates coherently through a metal. The ability to make levitons on demand could lead to the creation of quantum-electronics circuits that involve sending single electrons through tiny circuits.
Electrons in a metal or semiconductor can be thought of as a "Fermi sea" of particles, with the highest-energy electrons at the surface. Normally, if an electron receives an extra kick of energy it pops out of the Fermi sea, creating a "hole" – which is itself a quasiparticle. However, under special circumstances an electron (or a few electrons) can rise out of the Fermi sea without creating a hole – much like a wave rising out of the ocean. This excitation could then propagate through the material like a tiny particle that obeys quantum mechanics – a quasiparticle.
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