Spin-resolved topology and partial axion angles in three-dimensional insulators

• DOI: 10.1038/s41467-024-44762-w
• Publication Date: 2024-01-16T17:02:39Z
• Authors: Kuan-Sen Lin; Giandomenico Palumbo; Zhaopeng Guo; Yoonseok Hwang; Jeremy Blackburn; Daniel P. Shoemaker; Fahad Mahmood; Zhijun Wang; Gregory A. Fiete; Benjamin J. Wieder; Barry Bradlyn
• Keywords: 0301 basic medicine; Condensed Matter - Materials Science; Condensed Matter - Mesoscale and Nanoscale Physics; Strongly Correlated Electrons (cond-mat.str-el); Science; Q; Materials Science (cond-mat.mtrl-sci); FOS: Physical sciences; Article; Condensed Matter - Strongly Correlated Electrons; 03 medical and health sciences; Mesoscale and Nanoscale Physics (cond-mat.mes-hall); [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat]; [PHYS.COND.CM-MSQHE]Physics [physics]/Condensed Matter [cond-mat]/Mesoscopic Systems and Quantum Hall Effect [cond-mat.mes-hall]

AbstractSymmetry-protected topological crystalline insulators (TCIs) have primarily been characterized by their gapless boundary states. However, in time-reversal- ($${{{{{{{\mathcal{T}}}}}}}}$$ T -) invariant (helical) 3D TCIs—termed higher-order TCIs (HOTIs)—the boundary signatures can manifest as a sample-dependent network of 1D hinge states. We here introduce nested spin-resolved Wilson loops and layer constructions as tools to characterize the intrinsic bulk topological properties of spinful 3D insulators. We discover that helical HOTIs realize one of three spin-resolved phases with distinct responses that are quantitatively robust to large deformations of the bulk spin-orbital texture: 3D quantum spin Hall insulators (QSHIs), “spin-Weyl” semimetals, and $${{{{{{{\mathcal{T}}}}}}}}$$ T -doubled axion insulator (T-DAXI) states with nontrivial partial axion angles indicative of a 3D spin-magnetoelectric bulk response and half-quantized 2D TI surface states originating from a partial parity anomaly. Using ab-initio calculations, we demonstrate that β-MoTe2 realizes a spin-Weyl state and that α-BiBr hosts both 3D QSHI and T-DAXI regimes.