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; Hiroshi Murakawa; Noriaki Hanasaki; Hideaki Sakai

doi:10.1038/s43246-021-00152-z

arXiv · 2103.06765

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·Hiroshi Murakawa·Noriaki Hanasaki·Hideaki Sakai

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Abstract

In non-centrosymmetric metals, spin-orbit coupling (SOC) induces momentum-dependent spin polarization at the Fermi surfaces. This is exemplified by the valley-contrasting spin polarization in monolayer transition metal dichalcogenides (TMDCs) with in-plane inversion asymmetry. However, the valley configuration of massive Dirac fermions in TMDCs 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 in spite of the larger SOC, 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.

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Masaki Kondo, Masayuki Ochi, Tatsuhiro Kojima, Ryosuke Kurihara, Daiki Sekine, Masakazu Matsubara, Atsushi Miyake, Masashi Tokunaga, Kazuhiko Kuroki, Hiroshi Murakawa, Noriaki Hanasaki, Hideaki Sakai. 2021-03-11. Tunable spin-valley coupling in layered polar Dirac metals. https://doi.org/10.1038/s43246-021-00152-z

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