# Topological transport in Dirac nodal-line semimetals

## TL;DR

This paper explores the topological transport phenomena in Dirac nodal-line semimetals, revealing how inversion symmetry breaking induces a universal Hall-like current driven by the parity anomaly, with implications for device design.

## Contribution

It introduces the concept of electric-field induced anomalous transverse current in nodal-line semimetals, linking topological Berry phase effects to observable transport phenomena.

## Key findings

- Inversion breaking leads to a universal Hall-like current.
- Opposite sides of the Dirac ring carry opposite surface flows.
- Proposed a device to detect topological currents using surface states.

## Abstract

Topological nodal-line semimetals are characterized by one-dimensional Dirac nodal rings that are protected by the combined symmetry of inversion $\mathcal{P}$ and time-reversal $\mathcal{T}$. The stability of these Dirac rings is guaranteed by a quantized $\pm \pi$ Berry phase and their low-energy physics is described by a one-parameter family of (2+1)-dimensional quantum field theories exhibiting the parity anomaly. Here we study the Berry-phase supported topological transport of $\mathcal{P}\mathcal{T}$ invariant nodal-line semimetals. We find that small inversion breaking allows for an electric-field induced anomalous transverse current, whose universal component originates from the parity anomaly. Due to this Hall-like current, carriers at opposite sides of the Dirac nodal ring flow to opposite surfaces when an electric field is applied. To detect the topological currents, we propose a dumbbell device, which uses surface states to filter charges based on their momenta. Suggestions for experiments and device applications are discussed.