Symmetry-Forbidden Rectification via Dynamic Phase Transitions in the Weyl Metallic State of ZrTe.

Weyl metals, known for their topological structure and chiral anomaly, exhibit nonlinear transport that defies conventional theory. In this study, ZrTe, an inversion-symmetric Dirac semimetal tunable to a Weyl state by magnetic field, is investigated, and rectification (alternating current (AC) to direct current (DC) conversion) and third harmonic generation in longitudinal configurations is revealed. Despite its bulk inversion symmetry, symmetry-forbidden rectification and a dynamic phase transition arising from the chiral anomaly are observed. Rectification shows threshold behavior at a critical current density (𝐽) and temperature (𝑇* ≈ 30 K), while third-harmonic generation remains threshold-free. In transverse setups, even harmonics up to sixth order and a DC response, also symmetry-forbidden and threshold-sensitive, are detected. These results highlight the role of topology and dynamic symmetry breaking in enabling nonlinear responses and establish ZrTe as a model for terahertz and optoelectronic applications.