Magnetic field-induced type-II Weylsemimetallic state in geometrically frustrated Shastry-Sutherland lattice GdB4

TL;DR

This paper reports the discovery of a magnetic field-induced type-II Weyl semimetal state in the geometrically frustrated GdB4 crystal, revealing new topological electronic phases in frustrated magnetic systems.

Contribution

It demonstrates the emergence of a type-II Weyl semimetal in a frustrated antiferromagnetic lattice under magnetic fields, a novel finding in topological materials research.

Findings

Weyl nodes created above and below the Fermi energy under magnetic fields.

Detection of non-trivial Berry phase via de Haas-van Alphen experiments.

Observation of chiral-anomaly-induced negative magnetoresistance.

Abstract

Weyl semimetal is a topologically non-trivial phase of matter with pairs of Weyl nodes in the k-space, which act as monopole and anti-monopole pairs of Berry curvature. Two hallmarks of the Weyl metallic state are the topological surface state called the Fermi arc and the chiral anomaly. It is known that the chiral anomaly yields anomalous magneto-transport phenomena. In this study, we report the emergence of the type-II Weyl semimetallic state in the geometrically frustrated non-collinear antiferromagnetic Shastry-Sutherland lattice (SSL) GdB4 crystal. When we apply magnetic fields perpendicular to the noncollinear moments in SSL plane, Weyl nodes are created above and below the Fermi energy along the M-A line (tau-band) because the spin tilting breaks the time-reversal symmetry and lifts band degeneracy while preserving C4z or C2z symmetry. The unique electronic structure of GdB4 under magnetic fields applied perpendicular to the SSL gives rise to a non-trivial Berry phase, detected in de Haas-van Alphen experiments and chiral-anomaly-induced negative magnetoresistance. The emergence of the magnetic field-induced Weyl state in SSL presents a new guiding principle to develop novel types of Weyl semimetals in frustrated spin systems.