# Optical Control of Chiral Charge Pumping in a Topological Weyl Semimetal

## TL;DR

This study demonstrates optical control of chiral charge pumping in a Weyl semimetal using terahertz pulses, revealing long-lived chiral populations and potential for quantum optoelectronic applications.

## Contribution

It introduces a method to optically manipulate chiral charges in Weyl semimetals and measures their relaxation dynamics, advancing topological quantum control techniques.

## Key findings

- Chiral charge pumping can be optically controlled with terahertz pulses.
- Chiral population relaxation time exceeds 1 nanosecond.
- Long coherence times suggest potential for quantum technologies.

## Abstract

Solids with topologically robust electronic states exhibit unusual electronic and optical transport properties that do not exist in other materials. A particularly interesting example is chiral charge pumping, the so-called chiral anomaly, in recently discovered topological Weyl semimetals, where simultaneous application of parallel DC electric and magnetic fields creates an imbalance in the number of carriers of opposite topological charge (chirality). Here, using time-resolved terahertz measurements on the Weyl semimetal TaAs in a magnetic field, we optically interrogate the chiral anomaly by dynamically pumping the chiral charges and monitoring their subsequent relaxation. Theory based on Boltzmann transport shows that the observed effects originate from an optical nonlinearity in the chiral charge pumping process. Our measurements reveal that the chiral population relaxation time is much greater than 1 ns. The observation of terahertz-controlled chiral carriers with long coherence times and topological protection suggests the application of Weyl semimetals for quantum optoelectronic technology.