Endless Dirac nodal lines and high mobility in kagome semimetal Ni 3 In 2 Se 2 : a theoretical and experimental study.

Kagome-lattice crystal is crucial in quantum materials research, exhibiting unique transport properties due to its rich band structure and the presence of nodal lines and rings. Here, we investigate the electronic transport properties and perform first-principles calculations for Ni ₃ In ₂ Se ₂ kagome topological semimetal. First-principles calculations of the band structure without the inclusion of spin-orbit coupling (SOC) shows that three bands are crossing the Fermi level ( E _F ), indicating the semi-metallic nature. With SOC, the band structure reveals a gap opening of the order of 10 meV. Z ₂ index calculations suggest the topologically nontrivial natures ( ν ₀ ;ν1ν2ν3) = (1;111) both without and with SOC. Our detailed calculations also indicate six endless Dirac nodal lines and two nodal rings with a π -Berry phase in the absence of SOC. The temperature-dependent resistivity is dominated by two scattering mechanisms: s - d interband scattering occurs below 50 K, while electron-phonon ( e - p ) scattering is observed above 50 K. The magnetoresistance (MR) curve aligns with the theory of extended Kohler's rule, suggesting multiple scattering origins and temperature-dependent carrier densities. A maximum MR of 120% at 2 K and 9 T, with a maximum estimated mobility of approximately 3000 cm ² V ^-1 s ^-1 are observed. Ni ₃ In ₂ Se ₂ is an electron-hole compensated topological semimetal, as we have carrier density of electron ( n _e ) and hole ( n _h ) arene≈nh, estimated from Hall effect data fitted to a two-band model. Consequently, there is an increase in the mobility of electrons and holes, leading to a higher carrier mobility and a comparatively higher MR. The quantum interference effect leading to the two dimensional (2D) weak antilocalization effect (-σxx∝ln(B)) manifests as the diffusion of nodal line fermions in the 2D poloidal plane and the associated encircling Berry flux of nodal-line fermions.
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