(color online) Structural, superconducting, and Hall coefficient (R_H) phase diagram of black phosphorus at different pressures. (a) Pressure–temperature phase diagram combined with structural phase information. Here SM and SC_Rho-h represent semimetal and superconducting phases with rhombohedral structures and dominant hole carriers, respectively. SC_cubic-e and SC_cubic-h stand for the superconducting phase with cubic structure and dominance of electron carriers and hole carriers, respectively. TConset (R-1) and TConset (R-2) represent the onset temperature of superconducting transitions determined from resistance measurements for run 1 and run 2. T_C(ac) represents the superconducting transition temperature determined by ac susceptibility measurements. (b) Pressure dependent R_H measured at 15 K. The inset displays the detailed changes in R_H at the structural phase-transition boundaries. The pink and blue solid points represent Hall coefficients obtained from two independent runs. P_c1 and P_c2 stand for the critical pressures of the Lifshitz transitions. Reproduced with permission from Ref. [113].