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

摘要

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): Ba_2NaOsO_6, Sr_2SrOsO_6, and Ba_2BReO_6 (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 |x| = 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 Ba_2ZnReO_6 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 σ_(xy) of up to 1160 (Ω cm)~(-1). Our findings may apply widely for t_(2g) systems with cubic (or slightly distorted) fcc-like structures.