Extended Data Fig. 1: Longitudinal resistivity as a function of top gate voltage.
From: A unified realization of electrical quantities from the quantum International System of Units
Shown are measurements of QAHR longitudinal resistivity, ρxx, versus top gate voltage Vgate, performed with the CCC’s nanovoltmeter. First, Vgate was quickly swept toward negative voltages (blue circles, integration time τ = 10 s). Vgate was next brought back to zero and then swept toward positive voltages (orange squares, τ = 10 s). Each symbol represents an average of 30 observations per measurement. The time between measurements (symbols) was approximately 7 minutes. The curved arrows are intended as guides to the eye and show the sweep direction. Finally, Vgate was slowly swept over a narrow range (green crosses, τ = 60 s). For the narrow sweep, each symbol represents an average of 10 observations and the time between measurements was 12 minutes. The local minimum in ρxx seen near Vgate = 0 V indicates that the native Fermi level is well positioned near the center of the magnetic exchange gap. The mixing chamber temperature over the course of these sweeps (lasting about two hours total) only decreased by 0.2 mK. The decrease in ρxx near Vgate = 0 with each sweep suggests that either ρxx is strongly sensitive to temperature or that thermalization occurs over very long timescales.
