This paper investigates the electrical resistivity of EuCd₂As₂ under pressure, revealing an insulating dome between 1.0 GPa and 2.0 GPa, flanked by metallic transport regimes. This insulating state is fully suppressed by a small magnetic field, resulting in colossal negative magnetoresistance (~10⁻⁵). First-principles calculations attribute this resistivity behavior to consecutive transitions from a magnetic topological insulator to a trivial insulator, and finally to a Weyl semimetal, driven by pressure-induced changes in the magnetic ground state. The colossal magnetoresistance stems from a field-induced polarization of magnetic moments, transitioning the material from a trivial insulator to a Weyl semimetal. Weak exchange couplings and weak magnetic anisotropy are highlighted as crucial for realizing tunable magnetic topological materials.

Feng Du, Lin Yang, Zhi Yong Nie, Ninghua Wu, Yong Li, Shuaihua Luo, Ye Chen, Dajun Su, Michael Smidman, Youguo Shi, Chao Cao, Frank Steglich, Yu Song, Huiqi Yuan