Abstract
AbstractThe search for nontrivial superconductivity in novel quantum materials is currently a most attractive topic in condensed matter physics and material science. The experimental studies have progressed quickly over the past couple of years. In this article, we report systematic studies of superconductivity in Au2Pb single crystals. The bulk superconductivity (onset transition temperature, Tconset=1.3 K) of Au2Pb is characterised by both transport and diamagnetic measurements, where the upper critical field Hc2 shows unusual quasi-linear temperature dependence. The superconducting gap is revealed by point-contact measurement with gold tip. However, when using tungsten (W) tip, which is much harder, the superconducting gap probed is largely enhanced as demonstrated by the increases of both Tconset and upper critical field (Hc2). This can be interpreted as a result of increase in density of states under external anisotropic stress imposed by the tip, as revealed by first-principles calculations. Furthermore, novel phase winding of the pseudospin texture along k-space loops around the Fermi energy is uncovered from the calculations, indicating that the observed superconductivity in Au2Pb may have nontrivial topology.
Highlights
The recent discovery of three-dimensional (3D) Dirac semimetals,[1,2,3,4,5,6,7,8,9,10,11,12] as an intermediate state between a trivial insulator and a topological insulator, has stimulated extensive research on these materials
The superconductivity induced by hard point contact (PC) on Cd3As2 was recently reported and unconventional superconducting order parameter was suggested by the zero-bias conductance peak (ZBCP) and double conductance peaks (DCPs) symmetric around zero bias.[13,14]
By comparing the computed Fermi surfaces of Au2Pb of relaxed lattice structure and those under 1% uniaxial compression, we find that the Fermi surfaces are enlarged and the density of states near the Fermi energy increases under the applied external pressure, which agrees with the observed increase of Tconset in the PC measurements
Summary
The recent discovery of three-dimensional (3D) Dirac semimetals,[1,2,3,4,5,6,7,8,9,10,11,12] as an intermediate state between a trivial insulator and a topological insulator, has stimulated extensive research on these materials. The possibility of topological superconductivity is suggested by first-principles calculations, which show nontrivial topological properties of the projected pseudospin texture corresponding to the p- and d-orbitals near the Fermi energy, as well as the experimental observations of anomalous quasi-linear Hc2(T) behaviour and unusual PCS feature detected by W tip. These characteristics make Au2Pb a potential candidate material for topological superconductor
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