Evidence of magnetism-induced topological protection in the axion insulator candidate EuSn2P2

Gian Marco Pierantozzi; Alessandro De Vita; Chiara Bigi; Xin Gui; Hung-Ju Tien; Debashis Mondal; Federico Mazzola; Jun Fujii; Ivana Vobornik; Giovanni Vinai; Alessandro Sala; Cristina Africh; Tien-Lin Lee; Giorgio Rossi; Tay-Rong Chang; Weiwei Xie; Robert J Cava; Giancarlo Panaccione

doi:10.1073/pnas.2116575119

Evidence of magnetism-induced topological protection in the axion insulator candidate EuSn₂P₂

Proc Natl Acad Sci U S A. 2022 Jan 25;119(4):e2116575119. doi: 10.1073/pnas.2116575119.

Authors

Gian Marco Pierantozzi¹, Alessandro De Vita^{1

2}, Chiara Bigi¹, Xin Gui³, Hung-Ju Tien⁴, Debashis Mondal^{1

5}, Federico Mazzola¹, Jun Fujii¹, Ivana Vobornik¹, Giovanni Vinai¹, Alessandro Sala¹, Cristina Africh¹, Tien-Lin Lee⁶, Giorgio Rossi^{1

2}, Tay-Rong Chang^{4

7

8}, Weiwei Xie⁹, Robert J Cava¹⁰, Giancarlo Panaccione¹

Affiliations

¹ Istituto Officina dei Materiali, Consiglio Nazionale delle Ricerche, Trieste I-34149, Italy.
² Dipartimento di Fisica, University of Milano, Milano I-20133, Italy.
³ Department of Chemistry, Princeton University, Princeton, NJ 08544.
⁴ Department of Physics, National Cheng Kung University, Tainan 701, Taiwan.
⁵ International Centre for Theoretical Physics, Trieste I-34100, Italy.
⁶ Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, United Kingdom.
⁷ Center for Quantum Frontiers of Research and Technology, Tainan 701, Taiwan.
⁸ Physics Division, National Center for Theoretical Sciences, National Taiwan University, Taipei 10617, Taiwan.
⁹ Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854.
¹⁰ Department of Chemistry, Princeton University, Princeton, NJ 08544; rcava@princeton.edu.

Abstract

We unravel the interplay of topological properties and the layered (anti)ferromagnetic ordering in EuSn₂P₂, using spin and chemical selective electron and X-ray spectroscopies supported by first-principle calculations. We reveal the presence of in-plane long-range ferromagnetic order triggering topological invariants and resulting in the multiple protection of topological Dirac states. We provide clear evidence that layer-dependent spin-momentum locking coexists with ferromagnetism in this material, a cohabitation that promotes EuSn₂P₂ as a prime candidate axion insulator for topological antiferromagnetic spintronics applications.

Keywords: ARPES; axion insulator; magnetism; spin polarization; topological surface states.