The yellow-green area is where resonant THz absorption occurs, as measured by THz time-delay spectroscopy, using the discrete magnetic-field values shown in Fig. 2 . The data are corrected for experimental variations of the amplitude A from equation ( 1 ). The red-brown area is the low-temperature phase diagram inferred from a convolution of magnetotransport, magnetostriction and magnetization measurements 31 . Our spectroscopic results are consistent with the low-temperature phase diagram and extend it to high temperatures, showing non-Fermi liquid behaviour up to approximately 25 K, as expected. The critical breakdown of heavy quasiparticles is seen on the HF side of the QPT (bright yellow region for B > 66 mT), whereas no heavy quasiparticles are present on the antiferromagnetic side (dark green region for B < 66 mT). Figure adapted with permission from ref. 31 under a Creative Commons license CC BY.
