Abstract
Topological materials have drawn increasing attention owing to their rich quantum properties, as highlighted by a large intrinsic anomalous Hall effect (AHE) in Weyl and nodal-line semimetals. However, the practical applications for topological electronics have been hampered by the difficulty in the external control of the band topology. Here we demonstrate a magnetic-field-induced switching of band topology in $\alpha{\mathrm{-EuP}}_3$, a magnetic semimetal with a layered crystal structure derived from black phosphorus. When the magnetic field is applied perpendicular to the single mirror plane of the monoclinic structure, a giant AHE signal abruptly emerges at a certain threshold magnetization value, giving rise to a prominently large anomalous Hall angle of $\left|\Theta_{\mathrm{AHE}}\right| \sim 20^{\circ}$. When the magnetic field is applied along the inter-layer direction, which breaks the mirror symmetry, the system shows a pronounced negative longitudinal magnetoresistance. On the basis of electronic structure calculations and symmetry considerations, these anomalous magneto-transport properties can be considered as manifestations of two distinct topological phases: topological nodal-line and Weyl semimetals, respectively. Notably, the nodal-line structure is composed of bands with the same spin character and spans a wide energy range around the Fermi level. These topological phases are stabilized via the exchange coupling between localized Eu-4$f$ moments and mobile carriers conducting through the phosphorus layers. Our findings provide a realistic solution for external manipulation of band topology, enriching the functional aspects of topological materials.
Highlights
Topological semimetals (TSs) are a new class of quantum materials hosting nontrivial massless fermionic states, which are derived from linearly dispersing bands crossing at the Fermi level [1,2,3,4,5,6,7,8]
When the magnetic field is applied perpendicular to the single mirror plane of the monoclinic structure, a giant anomalous Hall effect (AHE) signal abruptly emerges at a certain threshold magnetization value, giving rise to a prominently large anomalous Hall angle of jΘAHEj ∼ 20°
Based on first-principles calculations and group-theoretic analysis, we show that such nontrivial anomalies in the magnetotransport properties are manifestations of two distinct topological phases: topological nodal-line and Weyl semimetals, respectively
Summary
Topological semimetals (TSs) are a new class of quantum materials hosting nontrivial massless fermionic states, which are derived from linearly dispersing bands crossing at the Fermi level [1,2,3,4,5,6,7,8]. TSs are further categorized into two groups—Weyl and Dirac types—depending on whether they lack or hold spin degeneracy throughout their Brillouin zone, respectively Owing to their relativistic nature, such band crossings generate a local but large internal magnetic flux, known as the Berry curvature, that can give rise to intriguing transport phenomena such as the intrinsic anomalous Hall effect (AHE) [9,10,11,12]. By controlling the time and space inversion symmetries, one such topological phase can, in principle, be turned into another This can be achieved by applying a magnetic field or via mechanical distortion, enabling practical approaches to exploiting the band topology and embedding. We introduce a magnetic semimetal, α-EuP3, with a simple, yet profoundly tunable electronic structure that ideally meets these criteria
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