Electronic and magnetic properties of the topological semimetal SmMg$_2$Bi$_2$

Asish K. Kundu; Santanu Pakhira; Tufan Roy; T. Yilmaz; Masahito Tsujikawa; Masafumi Shirai; E. Vescovo; D. C. Johnston; Abhay N. Pasupathy; Tonica Valla

doi:10.1103/physrevb.106.245131

arXiv · 2209.12109

Electronic and magnetic properties of the topological semimetal SmMg$_2$Bi$_2$

Asish K. Kundu·Santanu Pakhira·Tufan Roy·T. Yilmaz·Masahito Tsujikawa·Masafumi Shirai·E. Vescovo·D. C. Johnston·Abhay N. Pasupathy·Tonica Valla

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Abstract

Dirac semimetals show nontrivial physical properties and can host exotic quantum states like Weyl semimetals and topological insulators under suitable external conditions. Here, by combining angle-resolved photoemission spectroscopy measurements (ARPES) and first-principle calculations, we demonstrate that Zintl-phase compound SmMg$_2$Bi$_2$ belongs to the close proximity to a topological Dirac semimetallic state. ARPES results show a Dirac-like band crossing at the zone-center near the Fermi level ($E_\mathrm {F}$) which is further confirmed by first-principle calculations. Theoretical studies also reveal that SmMg$_2$Bi$_2$ belongs to a $Z_2$ topological class and hosts spin-polarized states around the $E_\mathrm {F}$. Zintl's theory predicts that the valence state of Sm in this material should be Sm$^{2+}$, however we detect many Sm-4$f$ multiplet states (flat-bands) whose energy positions suggest the presence of both Sm$^{2+}$ and Sm$^{3+}$. It is also evident that these flat-bands and other dispersive states are strongly hybridized when they cross each other. Due to the presence of Sm$^{3+}$ ions, the temperature dependence of magnetic susceptibility $\chi(T)$ shows Curie-Weiss-like contribution in the low temperature region, in addition to the Van Vleck-like behaviour expected for the Sm$^{2+}$ ions. The present study will help in better understanding of the electronic structure, magnetism and transport properties of related materials.

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Asish K. Kundu, Santanu Pakhira, Tufan Roy, T. Yilmaz, Masahito Tsujikawa, Masafumi Shirai, E. Vescovo, D. C. Johnston, Abhay N. Pasupathy, Tonica Valla. 2022-09-25. Electronic and magnetic properties of the topological semimetal SmMg$_2$Bi$_2$. https://doi.org/10.1103/physrevb.106.245131

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