[행사/세미나] [Colloquium] April 5(Wed.) Magnetism and Berry curvature in correlated intermetallic Weyl semimetals
- 물리학과
- 조회수3087
- 2023-03-30
5. Abstract: Weyl semimetal is a topologically non-trivial phase of matter with pairs of Weyl nodes in the k-space, which act as monopole and anti-monopole pairs of Berry curvature. Two hallmarks of the Weyl metallic state are the nontrivial topological properties called the Fermi arc and the chiral anomaly, giving rise to anomalous magneto-transport phenomena. In this study, we report the emergence of the type-II Weyl semimetallic state in the geometrically frustrated non-collinear antiferromagnetic Shastry-Sutherland lattice (SSL) GdB4 crystal. The unique electronic structure of GdB4 under magnetic fields applied perpendicular to the SSL gives rise to a non-trivial Berry’s phase, detected in de Haas-van Alphen experiments and chiral anomaly-induced negative magnetoresistance. The emergence of the magnetic field-induced Weyl state in SSL presents a new guiding principle to develop novel types of Weyl semimetals in frustrated spin systems.
As a second topic, we propose the coexistence of the Kondo effect in Weyl semimetal in disordered Mn-doped MnxVAl3. Dilute Mn-doping in type-II Dirac semimetal VAl3 increases the chemical potential so that Dirac point is close to the Fermi energy and lifts band degeneracy, leading to the Weyl semimetal phase transition. We observed a Kondo effect, confirmed by the resistivity minimum at TK = 40 K, and logarithmic increase of electrical resistivity, magnetic susceptibility, and specific heat divided by temperature with a significant Sommerfeld coefficient at low temperature. The angle-resolved magnetoresistance has revealed the negative longitudinal magnetoresistance below Kondo temperature due to chiral anomaly in Mn-doped MnxVAl3. At low temperature below Kondo temperature, the exchange interaction by RKKY interaction in MnxVAl3 breaks time-reversal symmetry even in Kondo screening, resulting in the topological phase transition from Dirac to Weyl semimetal. This research shows the coexistence of the Kondo effect and Weyl semimetallic state as well as the temperature-induced topological phase transition.