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Nature Physics 4, 270–271 (1 April 2008) | doi:10.1038/nphys925

Topological order: How spin splits the electron

Joel Moore

An electron in a vacuum seems to be an indivisible particle of charge –e and spin 1/2, but an electron moving in the active background of a solid can break up into excitations ('quasiparticles') that carry modified values of charge or spin. The most celebrated example is the fractional quantum Hall effect, recognized by the 1998 Nobel Prize: the combination of an applied magnetic field and the Coulomb repulsion between electrons confined to a plane gives a liquid ground state whose quasiparticles carry fractional charge.