As pointed out in Ref.307, the like

As pointed out in Ref.307, the likely explanation of the data of Fig. 86 is that one of the ohmic contacts used to measure the Hall voltage is disordered in the sense of B¨uttiker112 that not all edge channels have unit transmission probability into the voltage probe. The disordered contact can be modeled by a potential barrier in the lead with a height not below that of the barrier in the constriction, as illustrated in Fig. 87. A net current I flows through the constriction, determined by its two-terminal resistance according to I = (2e/h)Nminμs, with μs the chemical potential of the source reservoir (the chemical potential of the drain reservoir μd is taken as a zero reference). Equation (3.12) applied to the two opposite Hall probes l1 and l2 in Fig. 87 takes the form (using Il1 = Il2 = 0, μs = (h/2e)I/Nmin, and μd = 0)