Dear Kwant community,

I have been studying the integer quantum Hall effect using the Kwant
software, through which I computed the longitudinal and transverse
conductance of a central sample (without disorder) in a four-terminal setup.

I model the central device, which is subject to a strong magnetic field,
as a square of lateral length, L. Both the sample and the four ideal
leads are described by a square-lattice tight-binding model with
nearest-neighbor hoppings.

By computing the transverse conductance as a function of the Fermi
energy, so that the first two Landau levels are crossed, I observe the
expected behavior: the conductance appears quantized in integer steps of
e²/h. However, upon zooming in on each of the two plateaus, I notice
that the conductance does not converge immediately to the expected
value. Instead, it exhibits a rippling effect, which seems to be
dependent on the leads' cross-section, L_{Lead}.

This phenomenon is illustrated in the attached .pdf file, and I have
also included the code used to evaluate the conductance.

My question is whether this behavior is a numerical issue, or if it is
expected within the context of charge transport simulations in
four-terminal setups.

Thank you in advance,

Henrique Veiga