Physical Properties of Antiferromagnetic Topological Material EuAuAs

Magnetic topological materials exhibit extraordinary physical properties that can be exploited for futuristic electronic devices and high-end quantum computations. In the course of our efforts to identify new magnetic topological materials, we have recently characterized EuAgAs as an antiferromagnetic nodal line Dirac semimetal [1]. Here, we report for the first time on the physical properties of isostructural compound EuAuAs (sg. $P6_3/mmc$), studied on single crystals grown from Bi flux. The magnetic susceptibility data revealed an antiferromagnetic transition at $T_N$ = 6 K due to Eu$^{2+}$ ions. In the ordered state, the magnetization first increases linearly with increasing magnetic field strength and then saturates in high fields. The heat capacity shows a clear anomaly at $T_N$, accompanied by features suggesting short-range ordering. The temperature-dependent electrical resistivity data exhibits a metal-semiconductor-like transition near 40 K, which gets suppressed with the application of magnetic field. Below $T_N$, the transverse magnetoresistance shows a positive maximum, marking a metamagnetic transition, and in high magnetic fields, it saturates at a large negative value of about 80\%. The antiferromagnetic ground state in EuAuAs has been corroborated through our ab-initio electronic band structure calculations. Most importantly, the theoretical computations revealed the formation of a nodal line in the bulk structure, which is placed slightly above the chemical potential and protected by rotational crystal symmetry, as well as a drumhead-like surface state, located at high symmetry point. All these results consistently suggest that EuAuAs is a new candidate for antiferromagnetic nodal line Weyl semimetal.

[1] A. Laha et al., Phys. Rev. B 103, L241112 (2021).