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arXiv · 2603.21423

Colossal Terahertz Magnetoresistance from Magnetic Polarons in EuZn$_2$P$_2$

E. Marulanda·M. Dutra·N. M. Kawahala·E. D. Stefanato·G. G. Vasques·J. Munevar·M. A. Avila·F. G. G. Hernandez
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Abstract

Magnetic polarons can generate colossal magnetoresistance in magnetic semiconductors, yet their terahertz electrodynamics remain largely unexplored. Here we report magneto-terahertz spectroscopy of the Eu-based Zintl antiferromagnet EuZn$_2$P$_2$. The low-frequency conductivity shows pronounced non-Drude behavior consistent with an evolution from isolated to overlapping magnetic polarons upon cooling. The polaron relaxation time reaches a maximum near the N\'eel temperature at zero field and exhibits a strong magnetic-field dependence. This polaron-driven reshaping of the conductivity leads to a strongly frequency-dependent magnetoresistance that becomes colossal in the terahertz range, reaching about 90~\% at 1.5~THz, roughly three times larger than the zero-frequency limit value. These results demonstrate that magnetic polarons strongly govern the low-energy electrodynamics and highlight the sensitivity of terahertz spectroscopy to polaronic magnetotransport in correlated magnetic semiconductors.

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E. Marulanda, M. Dutra, N. M. Kawahala, E. D. Stefanato, G. G. Vasques, J. Munevar, M. A. Avila, F. G. G. Hernandez. 2026-03-22. Colossal Terahertz Magnetoresistance from Magnetic Polarons in EuZn$_2$P$_2$. https://arxiv.org/abs/2603.21423

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