Nonequilibrium quantum noise in chiral Luttinger liquids

We study nonequilibrium noise in chiral Luttinger liquids using the Landauer-Buttiker scattering approach, obtaining the current and voltage noise spectrum for a four-terminal measurement scheme. Experimental consequences of the tunneling of charges an present in the four-terminal measurement of both the low-frequency shot noise (omega near 0), and the high-frequency Josephson noise (omega near omega(j)=e*V/(S) over bar h). Within perturbation theory, an algebraic singularity is present at the Josephson frequency omega(j)=e*V/(S) over bar h, whose position depends on the charge e* of the tunneling particles, either electrons or fractionally charged quasiparticles. These two types of tunneling are related by a strong-weak-coupling duality transformation. We show in a nonperturbative calculation for an exactly solvable point that the singularity at the quasiparticle frequency exists only in the limit of vanishing coupling, whereas the singularity at the electron frequency is present for all coupling strengths. The vanishing coupling limit corresponds to perfectly quantized Hall conductance in the case of quasiparticle tunneling between edge states in the fractional quantum Hall regime, and thus tunneling destroys the singularity at the quasiparticle frequency concomitantly with the quantized current.