Quasi-two-dimensional relativistic fermions probed by de Haas–van Alphen quantum oscillations in LuSn2

We report de Haas--van Alphen (dHvA) quantum oscillation studies on a layered compound $\mathrm{Lu}{\mathrm{Sn}}_{2}$. Through the analyses of the dHvA oscillation data, we find this material has several 3D bands and one quasi-2D band hosting relativistic fermions. Compared to previously reported dHvA oscitations in $\mathrm{Y}{\mathrm{Sn}}_{2,}$, the oscillation component arising from the quasi-2D band is significantly enhanced. From structural analyses using single-crystal x-ray diffraction, we find the distorted Sn-square net layer is less corrugated than $\mathrm{Y}{\mathrm{Sn}}_{2,}$, which accounts for the enhancement of two dimensionality of the relativistic fermions created in this layer. This result suggests that the dimensionality of relativistic band in $\mathrm{RE}{\mathrm{Sn}}_{2}$ ($\mathrm{RE}=\mathrm{rare}$ earth) can be tuned by electronegativity of RE. Moreover, we also find the 3D relativistic bands are pushed closer to the Fermi level with respect to $\mathrm{Y}{\mathrm{Sn}}_{2,}$ due to enhanced spin-orbital coupling. These findings imply $\mathrm{RE}{\mathrm{Sn}}_{2}$ can be an interesting platform for seeking new topological states via the tuning of electronegativity, spin-orbital coupling, and magnetism.