When one “immerses” a particle in a quantum many-body system, for instance an electron in a solid, the particle “swims” shrouded by a cloud of excitations of its new environment. This composite object is called a quasiparticle and possesses the same features as the initial particle, but with modified physical properties ( mass, charge, etc... ).
As with other many-body phenomena, the ab initio calculation of quasiparticle properties is highly challenging, and in most cases it can only be treated approximately. To overcome this challenge, use of the versatility of laser-cooled gases to simulate many-body condensed matter systems has recently been proposed.
Writing in Physical Review Letters, André Schirotzek, Cheng-Hsun Wu, Ariel Sommer, and Martin Zwierlein from MIT in the US present a dramatic demonstration of this scheme by studying experimentally the behavior of an atomic impurity immersed in a Fermi sea of ultracold atoms: A very simple system that constitutes the epitome of quasiparticle physics.
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