arXiv subjects

P. Nikolić

Publications and source records attributed to P. Nikolić.

3 recordsLinked to original sources

arXiv2025

Incommensurate magnetic order drives singular angular magnetoresistance in a Weyl semimetal

We demonstrate that a multi-$\mathbf{k}$ incommensurate magnetic state in the Weyl semimetal CeAlGe gives rise to singular angular magnetoresistance (SAMR), an electrical-transport signature that detects the magnetic-field direction with exceptional precision. In contrast, the sister compound CeAlSi shows neither multi-$\mathbf{k}$ order nor SAMR. Both phenomena emerge upon $\sim57\%$ Ge substitution in CeAlSi$_{1-x}$Ge$_x$ and coincide with electronic-structure changes that soften the single-ion in-plane anisotropy and enhance Weyl-mediated magnetic interactions. These results reveal a direct connection between band topology, electronic transport, and collective magnetism in Weyl semimetals.

cond-mat.str-el↗

arXiv2020

Magnetic impurities in Kondo insulators: An application to samarium hexaboride

Impurities and defects in Kondo insulators can have an unusual impact on dynamics that blends with effects of intrinsic electron correlations. Such crystal imperfections are difficult to avoid, and their consequences are incompletely understood. Here we study magnetic impurities in Kondo insulators via perturbation theory of the s-d Kondo impurity model adapted to small bandgap insulators. The calculated magnetization and specific heat agree with recent thermodynamic measurements in samarium hexaboride (SmB$_6$). This qualitative agreement supports the physical picture of multi-channel Kondo screening of local moments by electrons and holes involving both intrinsic and impurity bands. Specific heat is thermally activated in zero field by Kondo screening through sub-gap impurity bands and exhibits a characteristic upturn as the temperature is decreased. In contrast, magnetization obtains a dominant quantum correction from partial screening by virtual particle-hole pairs in intrinsic bands. We point out that magnetic impurities could impact de Haas-van Alphen quantum oscillations in SmB$_6$, through the effects of Landau quantization in intrinsic bands on the Kondo screening of impurity moments.

cond-mat.str-el↗

arXiv2015

Interaction Driven Subgap Spin Exciton in the Kondo Insulator SmB6

Using inelastic neutron scattering, we map a 14 meV coherent resonant mode in the topological Kondo insulator SmB6 and describe its relation to the low energy insulating band structure. The resonant intensity is confined to the X and R high symmetry points, repeating outside the first Brillouin zone and dispersing less than 2 meV, with a 5d-like magnetic form factor. We present a slave-boson treatment of the Anderson Hamiltonian with a third neighbor dominated hybridized band structure. This approach produces a spin exciton below the charge gap with features that are consistent with the observed neutron scattering. We find that maxima in the wave vector dependence of the inelastic neutron scattering indicate band inversion.

cond-mat.str-el↗