Probing Ideal Weyl Semimetal Phases and Lifshitz Transitions in MnBi_2-xSb_xTe₄

Weyl semimetals (WSMs) are three-dimensional topological materials that exhibit fascinating properties due to the presence of Weyl nodes in their band structure. MnBi_2-xSb_xTe₄, an intrinsic magnetic topological material, has emerged as an ideal platform for studying Weyl physics due to its strong coupling between magnetism and electronic structure. In this talk, we reveal distinct changes in the Fermi surface topology and Berry curvature as a function of chemical doping, consistent with the theoretical predictions of an ideal type-II Weyl semimetal phase, as evidenced by quantum oscillation studies and high-field Hall measurements. Furthermore, we present experimental evidence for an in-situ controlled Lifshitz transition from a type-II to a type-I Weyl semimetal, achieved via the simple rotation of an external magnetic field. These findings highlight the potential of MnBi_2-xSb_xTe₄ as a versatile platform for probing topological phase transitions and shed light on the interplay between magnetism and topology.