Abstract
The experimental discovery of Weyl semimetals offers unprecedented opportunities to study Weyl physics in condensed matters. Unique electromagnetic response of Weyl semimetals such as chiral magnetic effect has been observed and presented by the axial θ E · B term in electromagnetic Lagrangian (E and B are the electric and magnetic field, respectively). But till now, the experimental progress in this direction in Weyl semimetals is restricted to the DC regime. Here we report experimental access to the dynamic regime in Weyl semimetal NbAs by combining the internal deformation potential of coupled phonons with applied static magnetic field. While the dynamic E · B field is realized, it produces an anomalous phonon activity with a characteristic angle-dependence. Our results provide an effective approach to achieve the dynamic regime beyond the widely-investigated DC limit which enables the coupling between the Weyl fermions and the electromagnetic wave for further study of novel light-matter interactions in Weyl semimetals.
Highlights
The experimental discovery of Weyl semimetals offers unprecedented opportunities to study Weyl physics in condensed matters
The θE · B presents a fundamental difference in electromagnetic response between Weyl semimetals and others, till most experimental progress related to θE · B such as chiral anomaly, was achieved in the DC limit where E · B is static
Having established a firm link between the phonon activity and the chiral anomaly in experiments, we discuss how the dynamic chiral magnetic effect is allowed for the crystal symmetry of NbAs
Summary
The experimental discovery of Weyl semimetals offers unprecedented opportunities to study Weyl physics in condensed matters. Our results provide an effective approach to achieve the dynamic regime beyond the widely-investigated DC limit which enables the coupling between the Weyl fermions and the electromagnetic wave for further study of novel light-matter interactions in Weyl semimetals. A series of controlled magneto-infrared experiments show that such a phonon activity is dependent on the relative angle between the magnetic field and the polarization direction of the light. These observations fully agree with our theory based on the symmetry analysis and the prediction of dynamic chiral anomaly[20,21,22]
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