Coexistence of Kondo Effect and Weyl Semimetallic States in Mn-Doped Mn_xVAl₃ Compounds

Topological Dirac and Weyl semimetals are a 3-dimensional topological phase of matter, exhibit gapless energy bands with bulk band crossing that lead to the linear band dispersion. Degenerated Dirac bands are separated by breaking of topological symmetries, resulting in the formation of Weyl semimetal. The strong correlation effect in topological Weyl semimetal is a critical issue in condensed matter physics. Recently, one of the strong correlation effect, the Kondo effect, in Weyl semimetal was theoretically proposed but not yet realized experimental point of view. Here we suggest a coexistence of the Weyl semimetal and Kondo effect in disordered Mn-doped Mn_xVAl₃. Dilute magnetic element Mn-doping in type-II Dirac semimetal VAl₃ acts as a magnetic impurities that induces the tuning of its chemical potential so the Dirac points go closer to the Fermi energy and lifts its band degeneracy, leading to the Weyl semimetal topological phase transition. We observed the Kondo effect by several experimental points of view. Especially, the Kondo effect has confirmed by the electrical resistivity minimum at T_K = 40 K, and logarithmic increase of electrical resistivity, magnetic susceptibility, and specific heat divided by temperature with a significant Sommerfeld coefficient at low temperature. Furthermore, in order to confirm the topological phase transition from Dirac to Weyl semimetal, we affirm the experimental suggstion of Weyl semimetallic phase. One of the representative confirmation of the Weyl semimetal is the angle-resolved magnetoresistance, which has revealed the negative longitudinal magnetoresistance below Kondo temperature due to the chiral anomaly in Mn-doped Mn_xVAl₃. At low temperature below Kondo temperature (T ≤ T_K), the exchange interaction by RKKY interaction in Mn_xVAl₃ breaks time-reversal symmetry even in Kondo screening, resulting in the topological phase transition from Dirac to Weyl semimetal. Also the angle-dependent planar Hall effect can manifests the nontrivial Berry phase of matter and the chiral anomaly which elucidates the same physical origin with negative longitudinal magnetoresistance. This research shows the coexistence of the Kondo effect and Weyl semimetallic state in experimental viewpoint as well as the temperature-induced topological phase transition.