Chemical doping and high-pressure studies of layered β-PdB i2 single crystals

We have systematically grown large single crystals of the layered compounds β-PdBi2, and both the hole-doped PdBi2-xPbx and the electron-doped NaxPdBi2, and studied their magnetic and transport properties. Hall effect measurements on PdBi2, PdBi1.8Pb0.2, and Na0.057PdBi2 show that the charge transport is dominated by electrons in all of the samples. The electron concentration is substantially reduced upon Pb doping in PdBi2-xPbx and increased upon Na intercalation in NaxPdBi2, indicating effective hole doping by Pb and electron doping by Na. We observed a monotonic decrease of the superconducting transition temperature (Tc) from 5.4 K in undoped PdBi2 to less than 2 K for x>0.35 in hole-doped PdBi2-xPbx. Meanwhile, a rapid decrease of Tc with Na intercalation is also observed in the electron-doped NaxPdBi2, which is in disagreement with the theoretical expectation. In addition, both the magnetoresistance and Hall resistance further reveal evidence for a possible spin excitation associated with Fermi surface reconstruction at ∼50 K in the Na-intercalated PdBi2 sample. The complete phase diagram is thus established from hole doping to electron doping. Meanwhile, a high-pressure study of the undoped PdBi2 shows that the Tc is linearly suppressed under pressure with a dTc/dP coefficient of -0.28 K/GPa.