Tunable spin-valley coupling in layered polar Dirac metals
Masaki Kondo, Masayuki Ochi, Tatsuhiro Kojima, Ryosuke Kurihara, Daiki Sekine, Masakazu Matsubara, Atsushi Miyake, Masashi Tokunaga, Kazuhiko Kuroki, H. Murakawa, Noriaki Hanasaki, Hideaki Sakai
Abstract
Abstract In non-centrosymmetric metals, spin-orbit coupling induces momentum-dependent spin polarization at the Fermi surfaces. This is exemplified by the valley-contrasting spin polarization in monolayer transition metal dichalcogenides with in-plane inversion asymmetry. However, the valley configuration of massive Dirac fermions in transition metal dichalcogenides is fixed by the graphene-like structure, which limits the variety of spin-valley coupling. Here, we show that the layered polar metal BaMn X 2 ( X = Bi, Sb) hosts tunable spin-valley-coupled Dirac fermions, which originate from the distorted X square net with in-plane lattice polarization. We found that BaMnBi 2 has approximately one-tenth the lattice distortion of BaMnSb 2 , from which a different configuration of spin-polarized Dirac valleys is theoretically predicted. This was experimentally observed as a clear difference in the Shubnikov-de Haas oscillation at high fields between the two materials. The chemically tunable spin-valley coupling in BaMn X 2 makes it a promising material for various spin-valleytronic devices.