Chemical doping and high pressure studies of layered beta-PdBi2 single crystals

TL;DR

This study systematically explores how chemical doping and high pressure influence the magnetic, transport, and superconducting properties of layered beta-PdBi2 single crystals, revealing doping effects on charge carriers and a pressure-induced suppression of Tc.

Contribution

It provides the first comprehensive phase diagram of beta-PdBi2 under both hole and electron doping, and investigates the effects of high pressure on its superconductivity.

Findings

Charge transport is dominated by electrons in all samples.

Superconducting Tc decreases with doping, more rapidly in Na-intercalated samples.

High pressure suppresses Tc linearly with a coefficient of -0.28K/GPa.

Abstract

We have systematically grown large single crystals of layered compound beta-PdBi2, both the hole-doped PdBi2-xPbx and the electron-doped NaxPdBi2, and studied their magnetic and transport properties. Hall-effect measurement on PdBi2, PdBi1.8Pb0.2, and Na0.057PdBi2 shows 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 the effective hole-doping by Pb and electron-doping by Na. We observed a monotonic decrease of superconducting transition temperature (Tc) from 5.4K in undoped PdBi2 to less than 2K for x > 0.35 in hole-doped PdBi2-xPbx. Meanwhile, a rapid decrease of Tc with the 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 density wave (SDW)-like transition below 50K in the Na-intercalated PdBi2 sample. The complete phase diagram is thus established from hole-doping to electron-doping. Meanwhile, high pressure study of the undoped PdBi2 shows that the Tc is linearly suppressed under pressure with a dTc/dP coefficient of -0.28K/GPa.