Precision quantum Hall resistance measurement on epitaxial graphene device in low magnetic field

Precision quantum Hall resistance (QHR) measurements were performed on large-area epitaxial graphene device at temperature T = 1.5 K and at magnetic fields B from 8 T down to 2.5 T, that is much lower than typically used in precision QHR measurement. QHR was measured using cryogenic current comparator resistance bridge with relatively large biasing current I sd = 41 µA to reduce measurement uncertainty. The results showed that at B = 8 T, the relative deviation of Hall resistance from the expected quantized value h/2e 2 is within experimental uncertainty of 3.5 parts in 108 and remained below 0.35 parts per million (ppm) down to B = 3 T.