Symmetry-protected spinful magnetic Weyl nodal loops and multi-Weyl nodes in 5d(n) cubic double perovskites (n=1, 2)

Abstract

Using both an effective three-band model and ab initio calculations, we have investigated various topological features in the cubic ferromagnetic 5d(1,)(2) systems showing large spin-orbit coupling (SOC): Ba2NaOsO6, Sr2SrOsO6, and Ba2BReO6 (B=Mg, Zn). In the presence of time-reversal symmetry (T), spinless Dirac nodal loops linked to each other at the W points appear in the mirror planes. Remarkably, breaking T leads to spinful magnetic Weyl nodal loops (MWNLs) that are robust even at large SOC and correlation strength U variation due to the combination of mirror symmetry and broken T. Additionally, there are two types of magnetic Weyl points with chiral charges vertical bar chi vertical bar = 1, 2 along the C-4v symmetry line, and another type-II MWNL encircling the zone center, that are dependent on U. Furthermore, the ferromagnetic Ba2ZnReO6 is an ideal half semimetal with MWNLs and magnetic Weyl nodes at the Fermi level without the interference of topologically trivial bulk states. These systems give rise to a remarkably large anomalous Hall conductivity sigma(xy) of up to 1160 (Omega cm)(-1). Our findings may apply widely for t(2g) systems with cubic (or slightly distorted) fcc-like structures.