The limitations of the QAHE (low critical temperatures and currents) are experimentally investigated by magneto-transport measurements, and a detailed metrological assessment of optimised QAHE devices over large ranges of temperature (from sub-K to above 1 K) and current (from nA to above 1 µA) and over a relevant range of external magnetic field (from zero to several tesla) will be provided. This experimental work, for the first time performed in a coordinated manner will target two directions: 

1. Investigation and extension of the operating margins and Hall resistance quantisation at highest possible accuracy levels on metrology-grade QAHE devices from magnetically doped TI materials. Particularly, the Hall resistance measurements at elevated temperatures (above 1 kelvin) and bias currents (above 1 µA) will tackle a physical regime in which − up to now − accurate QAHE resistance quantisation could not be realised/demonstrated. 

2. Magneto-transport measurements at highest possible accuracy levels on new, selected exploratory QAHE devices from novel QAHE materials developed in WP1, in case that the pre-characterisation magneto-transport measurements indicate viability (metrology-grade performance / quality) for such advanced measurements.