Fig. 3: Decoupled nematic and magnetic criticality in FeSe_1-xS_x.

a Renormalized A* coefficient (upper) and similarly renormalized B* coefficient (lower) as a function of pressure having rescaled A and B respectively by the pressure-induced change in ρ₀. b Similarly renormalized A′* coefficient as a function of pressure. c Schematic T = 0 phase diagram in the p-x plane showing the nematic and magnetic phase boundaries. Vertical arrows indicate the pressure-induced approach of the two studied samples to the magnetic quantum critical point and the pressure ranges over which A and A′* can be determined. The horizontal arrow represents tuning away from the nematic quantum critical point (NQCP) with increasing x (relevant to panel d). Near x = x_c, the nematic phase boundary is shown as a dashed line to reflect its putative weak first-order nature. d Variation of A_t^*, the total low-temperature T² coefficient at ambient pressure rescaled by the relative growth in the carrier density, and x beyond the nematic quantum critical point near x_c  ~ 0.17 (red dotted line) with data from this work and literature sources^33,36,37. The error bars represent the estimated uncertainty in both x and the reported coefficients. We have estimated the error in the values reported in this work to be 50% due to the constraints on sample size in a pressure cell and 30% elsewhere. The uncertainty in x has been assumed to be ±0.015 and representative of the typical variation in x within an individual batch of samples¹². See Supplementary Note 1 for details of the rescaling procedure. The dashed line is a guide to the eye.