Field manipulation of Weyl modes in an ideal Dirac semimetal

TL;DR

This study demonstrates how magnetic field tuning in an ideal Dirac semimetal can manipulate multiple Weyl modes, revealing new topological phenomena and potential for spintronic applications.

Contribution

It reports the first experimental realization of multiple Weyl modes in a single material through magnetic field control, advancing topological electron physics and spintronics.

Findings

Observation of gapped Weyl mode, Weyl nodal ring, and coupled Weyl mode.

Anomalous Hall effect linked to large Berry curvature in gapped Weyl mode.

Negative magnetoresistivity associated with chiral anomaly and Weyl nodal ring annihilation.

Abstract

The emergent Weyl modes with the broken time-reversal symmetry or inversion symmetry provide large Berry curvature and chirality to carriers, offering the realistic platforms to explore topology of electrons in three-dimensional systems. However, the reversal transition between different types of Weyl modes in a single material, which is of particular interest in the fundamental research in Weyl physics and potential application in spintronics, is scarcely achieved due to restriction of inborn symmetry in crystals. Here, by tuning the direction and strength of magnetic field in an ideal Dirac semimetal, Bi4(Br0.27I0.73)4, we report the realization of multiple Weyl modes, including gapped Weyl mode, Weyl nodal ring, and coupled Weyl mode by the magnetoresistivity measurements and electronic structure calculations. Specifically, under a magnetic field with broken mirror symmetry, anomalous Hall effect with step feature results from the large Berry curvature for the gapped Weyl mode. A prominent negative magnetoresistivity is observed at low magnetic field with preserved mirror symmetry and disappears at high magnetic field, which is correlated to the chiral anomaly and its annihilation of Weyl nodal ring, respectively. Our findings reveal distinct Weyl modes under the intertwined crystal symmetry and time-reversal breaking, laying the foundation of manipulating multiple Weyl modes in chiral spintronic network.