Bulk superconductivity and non-trivial band topology analysis of Pb₂Pd

Abstract

In this article, we report single crystal growth of superconducting binary compound Pb2Pd. The crystal is well characterized through X-Ray Diffraction (XRD), Selected Area electron diffraction (SAED), Transmission Electron Microscopy (TEM), Field emission Scanning electron Microscopy (FESEM) and X-Ray Photoelectron spectroscopy (XPS). The bulk superconducting nature of the synthesized crystal is determined through AC susceptibility and magneto-heat capacity measurements. The specific heat jump at superconducting transition suggests Pb2Pd to be a moderately coupled s-wave superconductor. The topological non-trivial character of Pb2Pd is evidenced through bulk electronic band structure and Z2 invariants, which are calculated under the protocols of Density Functional Theory (DFT). Surface states spectrum of Pb2Pd is also studied, which further claims Pb2Pd to have topological non-trivial band structure.

Termination dependence of the surface states in Pb$_{2}$Pd

“…The Pd and Pb atoms are located in the high symmetry Wyckoff positions 4a (0,0,0.25), and 8h (0.1630,0.6630,0), respectively. Here it should be noted that the experimentally obtained Pb atom position was (0.1643,0.6643,0), which is close to the theoretical one [29].…”

“…a body-centered tetragonal unit cell with Pd atoms at the body center. After the DFT optimization, the lattice constants were found to be a = b = 6.997 Å, and c = 5.920 Å, which are close to the experimentally reported values a = b = 6.863 Å, and c = 5.840 Å [29]. The Pd and Pb atoms are located in the high symmetry Wyckoff positions 4a (0,0,0.25), and 8h (0.1630,0.6630,0), respectively.…”

“…One such example is Pb 2 Pd, which was first recognized as a superconductor in 1962 [28]. Powder XRD measurements confirm realization of the I4/mcm space group [29]. System remained the same after Bi-doping and the cell volume monotonically increased with higher Bi content [30].…”

“…System remained the same after Bi-doping and the cell volume monotonically increased with higher Bi content [30]. Similarly to PdTe 2 [31], Pb 2 Pd exhibit conventional s-wave superconducting behavior of the specific heat jump at T c around 3 K [28,29,32].…”

“…For example, in case of PdTe 2 (with P 3m1 symmetry) the bulk Dirac point and topological surface states were reported [35][36][37][38]. Initial theoretical results also suggest topological properties in the case of Pb 2 Pd [29], however, this feature is yet to be studied properly. In this paper, we discuss the electronic properties of Pb 2 Pd (electronic bulk band structure, and termination dependence of the surface states).…”