Quantum-limit phenomena and band structure in the magnetic topological semimetal EuZn_2As_2

The interplay between magnetism and non-trivial topological band structures in magnetic topological insulators can give rise to further exotic physical phenomenon. Here, the authors investigate the magnetic and electronic properties of EuZn_2As_2 under high-magnetic fields and low-temperatures and discuss what the observations can tell us about the interplay between magnetism and electronic topology in this system. The interplay between magnetism and electronic topology in the quantum limit is a forefront subject of condensed matter physics. Here, we show the electronic and magnetic properties of layered antiferromagnet EuZn_2As_2 in pulsed magnetic fields up to 60 T and temperatures down to 0.6 K. By analyzing the quantum oscillations observed in the magnetoresistance (MR) and proximity detector oscillator (PDO) frequency, we find that (1) the oscillation frequency F = 46 ± 6 T for H // c and 42 ± 2 T for H // ab ; (2) the corresponding Berry phase is close to π for H // c , implying a nontrivial topology; and (3) the large linear MR occurs beyond the first Landau level, without any sign of saturation. From these observations, we conclude that the linear MR can be understood by considering diffusing cyclotron centers due to compressed Landau wavefunction, an emergent behavior in the quantum limit.