Observation of quasiparticles with one-fifth of an electron's charge

Abstract

1-3 of this behaviour invokes strong Coulomb interactions among the electrons that give rise to fractionally charged quasiparticles which can be regarded as non- interacting current carriers 1-5 . Previous studies 4,5 have demon- strated the existence of quasiparticles with one-third of an electron's charge, the same fraction as that of the respective fractional state. An outstanding ambiguity is therefore whether these studies measured the charge or the conductance. Here we report the observation of quasiparticles with a charge of e/5 in the 2/5 fractional state, from measurements of shot noise in a two- dimensional electron gas 4 . Our results imply that charge can be measured independently of conductance in the fractional quantum Hall regime, generalizing previous observations of fractionally charged quasiparticles. In the fractional quantum Hall (FQH) regime, the first Landau level is partly populated, or 'fractionally filled'. Laughlin's explana- tion of the FQH effect 1-3 involved the emergence of new, fractionally charged, quasiparticles. Shot-noise measurements 4,5 have confirmed