Evidence for a Magnetic-Field-Induced Ideal Type-II Weyl State in Antiferromagnetic Topological Insulator Mn(Bi1−xSbx

The discovery of Weyl semimetals (WSMs) has fueled tremendous interest in condensed matter physics. The realization of WSMs requires the breaking of either inversion symmetry (IS) or time-reversal symmetry (TRS). WSMs can be categorized into type-I and type-II WSMs, which are characterized by untilted and strongly tilted Weyl cones, respectively. Type-I WSMs with breaking of either IS or TRS and type-II WSMs with solely broken IS have been realized experimentally, but a TRS-breaking type-II WSM still remains elusive. In this article, we report transport evidence for a TRS-breaking type-II WSM observed in the intrinsic antiferromagnetic topological insulator Mn(Bi1−xSbx)2Te4 under magnetic fields. This state is manifested by the electronic structure transition caused by the spin-flop transition. The transition results in an intrinsic anomalous Hall effect and negative c-axis longitudinal magnetoresistance attributable to the chiral anomaly in the ferromagnetic phases of lightly hole-doped samples. Our results establish a promising platform for exploring the underlying physics of the long-sought, ideal TRS-breaking type-II WSM.Received 21 June 2020Revised 25 April 2021Accepted 8 June 2021DOI:https://doi.org/10.1103/PhysRevX.11.031032Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasAnomalous Hall effectMagnetotransportTopological insulatorsTopological materialsTopological phase transitionPhysical SystemsAntiferromagnetsSingle crystal materialsWeyl semimetalTechniquesAngle-resolved photoemission spectroscopyCrystal growthDC susceptibility measurementsEnergy spectroscopy for chemical analysisHall barMagnetization measurementsResistivity measurementsShubnikov-de Haas effectX-ray diffractionCondensed Matter, Materials & Applied Physics