  Charge fractionalization is a possible emergent excitation in a
low-dimensional system of interacting electrons. A known example is that of
fractional charges in the fractional quantum Hall effect (FQHE) regime, which
is a consequence of strong Coulomb interaction among the electrons whose
kinetic energy is quenched by the strong magnetic field. Alternatively, the
integer QHE (IQHE), with electrons behaving largely as independent particles in
Landau levels (LLs), lacks such fractionalization. However, for integer LLs
filling v=2, 3,... electrons propagate in copropagating adjacent chiral edge
channels, and thus interact and modify the non-interacting LLs. For example, at
v=2, an electron injected selectively into a single non-interacting (bare) edge
channel is expected to decompose into a 'fast' mode and a 'slow' mode in the
region of interaction; each mode carry fractional charges shared between the
two bare channels. Here, we report our sensitive shot noise measurement that
affirms the presence of such fractionalization in v=2. Injecting partitioned
current into a 'hot' edge channel led to low frequency shot noise in the
adjacent currentless 'cold' edge channel after it had been partitioned.
Controlling the partitioning of the hot and cold channels allowed a
determination of the fractional charges in both channels as well as the
channels' velocity difference. This approach can be easily extended to study
interaction in two-dimensional systems with a topology dictating edge channels
transport.
