Low Carrier Density Metal Realized in Candidate Line-Node Dirac Semimetals CaAgP and CaAgAs

TL;DR

This study investigates polycrystalline CaAgP and CaAgAs, identifying their low-carrier metallic nature and ring-torus Fermi surfaces, with CaAgAs being more suitable for exploring line-node Dirac semimetal physics.

Contribution

It provides experimental and theoretical evidence of the electronic structures of CaAgP and CaAgAs as line-node Dirac semimetals with low carrier densities.

Findings

Both samples are low-carrier metals with hole dominance.

Fermi surfaces form a ring-torus shape from ring-shaped Dirac line nodes.

CaAgAs's Fermi energy is well-positioned for studying Dirac semimetal physics.

Abstract

We study polycrystalline samples of the hexagonal pnictides, CaAgP and CaAgAs, both of which are ideal candidates for line-node Dirac semimetals. The polycrystalline samples of CaAgP and CaAgAs obtained in this study are low-carrier metals, where hole carriers are dominant. By combining the hole carrier densities estimated from Hall coefficients and the electronic structures calculated by first principles calculations, both samples are found to have a ring-torus Fermi surface, derived from a ring-shaped Dirac line node. In the phosphide sample, the Fermi energy EF is located at around the end of the linear dispersion region of the electronic bands, while the EF in the arsenide sample exists in the middle of this region, suggesting that the arsenide is a more promising system for uncovering the physics of line-node Dirac semimetals.