Understanding topological matter in the fractional quantum Hall (FQH) effect
requires identifying the nature of edge state quasiparticles. FQH edge state at
the filling factor ν=2/3 in the spin-polarized and non-polarized phases is
represented by the two modes of composite fermions (CF) with the parallel or
opposite spins described by the chiral Luttinger liquids. Tunneling through a
quantum point contact (QPC) in such systems between different or similar spin
phases is solved exactly. With the increase of the applied voltage, the QPC
conductance grows from zero and saturates at e2/2h while a weak electron
tunneling between the edge modes with the same spin transforms into a
backscattering carried by the charge q=e/2 quasiparticles. These unusual
quasiparticles and conductance plateau emerge in the QPC with one or two CF
modes scattering into a single mode, as occurs in these systems. We propose
experiments on the applied voltage and temperature dependence of the QPC
conductance and noise that can shed light on the nature of edge states and FQH
transport.Comment: 6 pages, 1 figure + 4-page supplementary material in a single fil