Extended Data Fig. 1: Thermopower measurements in the fractional quantum Hall regime in device no. 3.
From: Detection of fractional quantum Hall states by entropy-sensitive measurements
a, The longitudinal thermal voltage Vxx (left axis) and Rxx (right axis) vs filling factor ν measured at B = 9 T and T = 1.64 K between pair 1 in device no. 3 (see e). While FQH states appear around filling factors 5/2 and 7/5 in Rxx, more FQH states are observable in Vxx. The temperature gradient was not calculated in this device due to a broken thermometer contact at base temperature. Therefore, the thermal voltage Vxx is plotted instead of thermopower. b, Landau fan of Vxx as a function of filling factor ν and magnetic field B at T = 300 mK measured between pair 1 in device no. 3 see e). In this plot the QH states appear as vertical lines at specific filling factors. In addition to integer QH states, FQH states at fractional fillings of 1/2, 4/5, 7/5, 5/2 and 8/3 are observable consistent with minima observed in a. c, Thermal voltage Vxx vs ν measured at B = −7.85 T and T = 300 mK between pair 2 in device no. 3 (see e). d, Landau fan of Vxx as a function of filling factor ν and magnetic field B measured at T = 300 mK between pair 2 showing vertical lines at fractional fillings including strong even denominator FQH states at 1/2 and 5/2 and odd denominator states consistent with those labeled in c. e, Optical image of a bilayer graphene thermopower device no. 3. Arrows show local thermometers and various electrode pairs used in measurements. f, Vxx and Vxy vs magnetic field B measured at fixed density of n = 0.99 × 1011 cm−2 at T = 300 mK between pair 1 showing a strong FQH state at ν = 5/2 specified by a minimum in Vxx (left axis) and a linear slope in Vxy (right axis) at this filling factor (see blue oval region). Only the strongest features are labeled.
