Band structure and charge ordering of Dirac semimetal EuAl4 at low temperatures

EuAl4 is proposed to host topological Hall state. This material also undergoes four consecutive antiferromagnetic (AFM) transitions upon cooling below T-N1= 15.4 K in the presence of charge density wave (CDW) order that sets in below T-CDW= 140 K. We use angle-resolved photoemission spectroscopy (ARPES) and density-functional-theory (DFT) calculations to study how magnetic ordering affects the electronic properties in EuAl4. We found changes in the band structure upon each of the four consecutive AFM transitions including band splitting, renormalizations and appearance of new bands forming additional Fermi sheets. In addition we also found significant enhancement of the quasiparticles lifetime due to suppression of spin flip scattering, similar to what was previously reported for ferromagnetic EuCd2As2. Surprisingly, we observe that most significant changes in electronic properties occurs not at T-N1, but instead at the AFM3 to AFM4 transition, which coincides with largest drop in resistivity.