Anomalous Residual Surface Conductivity in a Superconductor with Strong Spin-Orbit Coupling

Abstract

Conventional BCS superconductors are expected to exhibit a conductivity with vanishing dissipation with decreasing temperature. While bulk physical properties measurements indicate PdPb2 is a conventional superconductor with a Tc of 3.0 K, measurements of surface impedance through the microwave cavity perturbation technique indicate a large, non-vanishing dissipative component below Tc that is at odds with conventional superconductivity. We demonstrate PdPb2 to be a possible topological superconductor with a fully gapped bulk and a dissipative Majorana fluid surface.

Bulk superconductivity and non-trivial band topology analysis of Pb2Pd

“…The same Z2 index is reported for Bi 2 Te 3 , which is considered as a strong topological material [50]. Recently, another group [48] has reported the same non-trivial Z2 index υ 0 = 1 using a different methodevaluating the band parity at high symmetric time reversal invariant momenta points Γ and M [51]. Thus, on the basis of theoretical calculations, it can be concluded that Pb 2 Pd has strong non-trivial band topology.…”

“…Here, an exercise is made to determine the nature of superconductivity in Pb 2 Pd, as the ref. [26] shows the same to be type-I superconductor while it is shown to be of type-II in a very recent report [48]. Here, nature of superconductivity in synthesized Pb 2 Pd crystal is determined by calculating Ginzberg Landau Kappa (κ) parameter.…”

Sn2Pd: a possible superconducting material with topological surface states

“…Sb2Pd is superconducting below 1.35K with topological non-trivial band structure [22][23][24][25][26]. Another compound Pb2Pd is also superconducting and the theoretical calculations show the same to be a topological material [27][28][29]. Simultaneous existence of superconductivity with topological non-trivial band structure makes this family of compounds interesting.…”

“…TSMs having the general formula X 2 Pd (X = Bi, Pb, Sb) are reported to have topological non-trivial band structure along with bulk superconductivity [19][20][21][22][23][24][25][26][27][28][29]. β-Bi 2 Pd is extensively studied for its topological and superconducting properties [19][20][21].…”

“…The other members of this family viz. Pb 2 Pd and Sb 2 Pd are lesser studied [22][23][24][25][26][27][28][29]. Sb 2 Pd is superconducting below 1.35 K with topological non-trivial band structure [22][23][24][25][26].…”