Large topological Hall effect in a chiral antiferromagnet in hopping transport regime

The combination of structural chirality and magnetism leads to the formation of spin chirality through noncoplanar magnetic structures, resulting in unusual electronic transport properties. The spin chirality generates nonzero Berry curvature in real space, acting as an emergent magnetic field and contributing to the unconventional anomalous Hall effect, known as the geometrical or topological Hall effect (THE). This study unveils the remarkable occurrence of THE in a chiral antiferromagnetic (AFM) semiconductor <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mi>Eu</a:mi><a:msub><a:mi>Ir</a:mi><a:mn>2</a:mn></a:msub><a:msub><a:mi mathvariant="normal">P</a:mi><a:mn>2</a:mn></a:msub></a:mrow></a:math> in the hopping regime. It exhibits a complex incommensurately spiral AFM ground state due to its chiral crystalline structure, providing fertile ground for the emergence of topologically nontrivial spin textures such as skyrmions. A substantial THE is observed under finite magnetic fields, making <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:mrow><c:mi>Eu</c:mi><c:msub><c:mi>Ir</c:mi><c:mn>2</c:mn></c:msub><c:msub><c:mi mathvariant="normal">P</c:mi><c:mn>2</c:mn></c:msub></c:mrow></c:math> an exceptional case within the ultralow-conductivity hopping regime for investigating the interplay between topologically nontrivial magnetic structures and hopping carriers. Owing to its semiconducting nature, we have formulated a theoretical model based on Mott's variable range-hopping mechanism, effectively elucidating the temperature and magnetic field-dependent behavior of THE. <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"><e:mrow><e:mi>Eu</e:mi><e:msub><e:mi>Ir</e:mi><e:mn>2</e:mn></e:msub><e:msub><e:mi mathvariant="normal">P</e:mi><e:mn>2</e:mn></e:msub></e:mrow></e:math> thus serves as an ideal candidate for comprehending transport properties in the hopping regime and offers a unique opportunity for the implementation of AFM semiconductor-based spintronic devices. Published by the American Physical Society 2024