Quantum shot noise in edge channels

Charge excitations under quantized magnetic field flow in one dimensional‐like strips along the edges of the sample. These excitations (quasiparticles) may behave independently (under weaker fields) or condense to an interacting chiral Luttinger liquid (under stronger fields). Adding a backscattering potential in the path of the quasiparticles, partitions them, hence inducing quantum shot noise that is proportional to their charge and is affected by their correlation. We summarize here our studies of the noise in edge states. At sufficiently low temperatures the correlations among the scattering events are strong, leading to highly non‐linear I – V characteristic and non‐classical shot noise. However, at finite temperatures and weak back scattering, quasiparticles backscatter independently, with noise proportional to e /3, e /5 and e /7 at filling factors 1/3, 2/5, and 3/7. Alternatively, at sufficiently strong backscattering induced bunching of e /3 quasiparticles takes place, with shot noise proportional to e . Diluting the impinging quasiparticles beam mimics an increased temperature, effectively weakening the correlation, rendering the quasiparticles scattering stochastic. Moreover, surprisingly, at finite temperatures (∼50 mK), highly dilute fractionally charged quasiparticle beams are found to traverse almost opaque barriers with no significant bunching. Bunching, however, takes place at lower temperatures. In the opposite case of very weak backscattering potential and at extremely low temperatures (∼9 mK), surprising bunching of quasiparticles takes place: e * = 2 e /5 at filling factor 2/5 and e * close to 3 e /7 at filling factor 3/7. Under the same conditions, as the temperature increases, (to 25–50 mK) bunching ceases and the scattered charge is again the familiar Laughlin's quasiparticles charge e/m . We show also the shot noise generated by an edge channel interferometer. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)