Band inversion and pairing of high-spin quasiparticles induced by spin-orbit coupling
Dr. Kefeng Wang
Department of Physics and Center for Quantum Material Synthesis
Topological semimetals and metals, characterized by its touching conduction and valence bands, have emerged as a new frontier in the field of quantum materials. Novel macroscopic quantum phenomena they exhibit are not only of fundamental interest but may hold some potential for technological applications. When the spin-orbit coupling is strong enough to rearrange the order of electronic energy bands, various topological phases arise, and the interplay between superconductivity, transport behavior, and the topologically ordered phase is of particular interest. Here I will talk about our recent work on two kinds of topological semimetals. In a complete study of the ternary half-Heusler series R(Pd,Pt)Bi (R: rare earth), tuning of the rare earth f-electron component allows for simultaneous control of both lattice density and the strength of magnetic interaction. A controllable tuning of the normal-state band inversion strength, noncentrosymmetric superconducting pairing, and magnetically ordered ground states in this very interesting and versatile material points toward a unique and rich opportunity to realize both predicted and new exotic excitations in topological materials. We show evidence of unconventional superconductivity emerging from a spin-3/2 quasiparticle electronic structure in the topological half-Heusler semimetal YPtBi based on the linear temperature dependence of the London penetration depth, directly explained by a mixed-parity Cooper pairing model with a high-spin fermionic superfluid state. In another topological semimetal RhSb3, we observed an extremely large magnetoresistance which is widely observed in topological insulator and Dirac/Weyl semimetals. Our results suggest RhSb3 is a new class of zero-gap topological semimetal with linear energy dispersion.