Superconductivity in topologically nontrivial material Au2Pb

Abstract

The 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 characterized 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

Pressure-induced superconductivity in the three-dimensional topological Dirac semimetal Cd3As2

“…It may come from a two-band Fermi surface topology as in MgB 2 , [35][36][37] or an unconventional superconducting state as in heavy-fermion compound UBe 13 . 38 11,[39][40][41] We notice that no superconductivity was observed up to 13.43 GPa in an earlier pressure study of Cd 3 As 2 single crystal. 42 The reason may be that their sample is slightly different from ours, and pressure higher than 13.43 GPa is needed to induce superconductivity.…”

Fully gapped superconducting state in Au 2 Pb: A natural candidate for topological superconductor

“…More recently, it was argued that the cubic Laves phase Au 2 Pb (T c ≈ 1.2 K) may be another natural TSC candidate [25,26]. Electronic band structure calculations predicted that cubic Au 2 Pb has a bulk Dirac cone at room temperature [25].…”

“…In Ref. [26], the firstprinciples calculations also point to the nontrivial topology of the orbital texture near the dominant Fermi surfaces, which suggests the possibility of topological superconductivity. To check whether Au 2 Pb is indeed a TSC, it will be very important to determine its superconducting gap structure first.…”

“…-Single crystals of Au 2 Pb were grown by a self-flux method [26]. The sample for transport measurements was cut to a rectangular shape of dimensions 2.5 × 1.0 mm 2 in the ab plane, with a thickness of 0.10 mm along the c axis.…”

Unconventional superconductors with spin-orbit interaction

“…Au 2 Pb exhibits superconductivity at T c = 1.2K [123]. This material has also shown the ZBCP in the point contact spectra [122]. The above two Dirac semimetals are type I Dirac semimetals.…”