Anisotropic transport and optical spectroscopy study on antiferromagentic triangular lattice EuCd_2As_2: an interplay between magnetism and charge transport properties

TL;DR

This study investigates EuCd_2As_2, revealing its low carrier density semimetal nature, strong magnetic scattering effects, and the interplay between magnetism, charge transport, and lattice vibrations through anisotropic transport and optical spectroscopy.

Contribution

It provides new insights into the anisotropic charge and magnetic interactions in EuCd_2As_2, highlighting the coupling between phonons and electronic states near the antiferromagnetic transition.

Findings

EuCd_2As_2 is a low carrier density semimetal with anisotropic resistivity.

Resistivity shows a Kondo-like increase at low temperatures due to magnetic scattering.

Antiferromagnetic order reduces scattering, causing a sharp resistivity drop below 9.5 K.

Abstract

We present anisotropic transport and optical spectroscopy studies on EuCd_2As_2. The measurements reveal that EuCd_2As_2 is a low carrier density semimetal with moderate anisotropic resistivity ratio. The charge carriers experience very strong scattering from Eu magnetic moments, resulting in a Kondo-like increase of resistivity at low temperature. Below the antiferromagnetic transition temperature at $T_N$= 9.5 K, the resistivity drops sharply due to the reduced scattering from the ordered Eu moments. Nevertheless, the anisotropic ratio of $\rho_c/\rho_{ab}$ keeps increasing, suggesting that the antiferromagnetic coupling is along the c-axis. The optical spectroscopy measurement further reveals, besides an overdamped reflectance plasma edge at low energy, a strong coupling between phonon and electronic continuum. Our study suggests that EuCd_2As_2 is a promising candidate displaying intriguing interplay among charge, magnetism and the underlying crystal lattice.