Fractional Electromagnetic Response in Three-Dimensional Chiral Anomalous Semimetal

TL;DR

This paper reports the discovery of a fractional magnetoelectric effect in three-dimensional chiral anomalous semimetals, revealing a quarter-quantized topological response related to the band structure's winding number.

Contribution

It introduces the concept of fractional electromagnetic response in 3D chiral anomalous semimetals, linking it to the band topology and proposing experimental detection methods.

Findings

Fractional magnetoelectric effect with quarter-quantization.

Relation to the band structure's winding number 1/2.

Potential experimental platform using ZrTe5.

Abstract

The magnetoelectric coupling of electrons in a three-dimensional solid can be effectively described by axion electrodynamics. Here we report the discovery of the fractional magnetoelectric effect in chiral anomalous semimetals of the three-dimensional massless Wilson fermions, which have linear dispersions at the energy crossing point, and break the chiral symmetry at generic momenta. In the presence of electric and magnetic fields, the time-reversal and parity symmetry breaking give rise to the quarter-quantized topological magnetoelectric effect, which is directly related to the winding number 1/2 of the band structure, and is only one half of that for topological insulators. The fractional electromagnetic response can be revealed by the surface Hall conductance and extracted from the measurement of the topological Kerr and Faraday rotation. The transition-metal pentatelluride \mathrm{ZrTe_{5}} with a strain-tunable band gap provides a potential platform to test the effect experimentally.