Fig. 2: Extraction of composite fermion effective mass from C/T and entropy.

Temperature dependence of C/T at ν = 5/2 with corresponding relative filling factors ν^* = 0 and ν^* = ±0.0024. Upper panels: specific heat data is shown with blue circles and the blue curve is a guide-to-the-eye. The blue-shaded region is an uncertainty bound. The dashed blue line denotes the limiting value of C/T in the Fermi liquid phase. The solid green line is the C/T extracted from thermopower data shown in the inset by green crosses²⁷. Its limiting value in the Fermi liquid phase is shown by the green dashed line. From the limiting values denoted by the green and blue dashed lines, composite fermion mass was estimated (see main text). The red dashed line shows the Fermi liquid limiting value if the effective mass m^* = m_e. Lower panels: same data as the upper panels but with the blue-shaded area depicting the total entropy from 0 to 200 mK from which the effective mass can also be estimated (see main text). The red-hatched region depicts graphically the total entropy from 0 to 200 mK if the effective mass m^* = m_e. The error bars for the specific heat are showing the statistical errors propagated from the measurements of τ and K, see the Supplementary Information (SI) section 9. The error bars in thermopower data denote the uncertainty extracted from the local noise.