Evidence for three-dimensional Dirac semimetal state in strongly correlated organic quasi-two-dimensional material

TL;DR

This paper reports the discovery of a three-dimensional Dirac semimetal state in a strongly correlated organic material, demonstrating phenomena like chiral anomaly-induced negative magnetoresistance and planar Hall effect, influenced by electronic correlations.

Contribution

It provides experimental evidence of a 3D Dirac semimetal state in a molecule-based quasi-2D system with strong correlations, highlighting the role of dimensionality and correlations in topological states.

Findings

Observation of negative magnetoresistance due to chiral anomaly

Detection of planar Hall effect in the material

Strong electronic correlations break time-reversal symmetry

Abstract

The three-dimensional Dirac semimetal is distinct from its two-dimensional counterpart due to its dimensionality and symmetry. Here, we observe that molecule-based quasi-two-dimensional Dirac fermion system, $\alpha$-(BEDT-TTF)$_2$I$_3$, exhibits chiral anomaly-induced negative magnetoresistance and planar Hall effect upon entering the coherent inter-layer tunneling regime under high pressure. Time-reversal symmetry is broken due to the strong electronic correlation effect, while the spin-orbit coupling effect is negligible. The system provides an ideal platform for investigating the chiral anomaly physics by controlling dimensionality and strong electronic correlation.