Endless Dirac nodal lines and high mobility in kagome semimetal Ni₃In₂Se₂ : a theoretical and experimental study

Abstract

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 Ni3In2Se2 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 (EF ), indicating
the semi-metallic nature. With SOC, the band structure reveals a gap opening
of the order of 10 meV. Z2 index calculations suggest the topologically nontrivial
natures (ν0;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 electronphonon (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 cm2V−1
s
−1 are observed.
Ni3In2Se2 is an electron-hole compensated topological semimetal, as we have carrier
density of electron (ne) and hole (nh) are ne≈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
magnetoresistance. 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.