Fig. 4: Continuous exciton Mott transition in BP.
From: Quantum criticality of excitonic Mott metal-insulator transitions in black phosphorus
a Temperature dependence of integrated photocurrent at different excitation powers. 100% P = 160 W/cm2. b Photocurrents in a normalized to the maximum value at each excitation power. The curves are vertically offset to align the value at EG crossover temperature (220 K, indicated by black arrow) for clarity. The curves display three different branches, showing unconventional metallic properties near the transition boundary. c Phase diagram described in terms of the exponent of T-dependent resistivity extracted from our transport measurements as a function of T and pair density. The diagram clearly features a transition between the insulating phase with a negative coefficient (red) and the metallic phases with a positive coefficient (blue). At the intermediate region, T-linear resistivity is observed at low temperatures. Further, into the metal, the resistance starts to develop T2 behavior. The dashed lines are the boundaries of the IM region in Fig. 3a, showing an agreement between transport and spectral phase transitions. The shaded area indicates the inaccessible region in the temperature and e–h pair density space. d Log–log plots of resistivity (circles) versus temperature (below crossover temperature) as well as quadratic (blue) and linear (red) fits for different e–h pair densities near the transition boundary. The blue and red lines are the reference for the T and T2 trends. Source data of all figures are provided as a Source Data file.
