For several decades the low carrier density local moment magnet EuB6 has been considered a candidate material for ferromagnetic polarons. There is however no consistent explanation for the host of intriguing observations that have accrued over the years, including a prominently non-monotonic resistivity near Tc, and observation of spatial textures, with a characteristic spatial and energy scale, via scanning tunneling spectroscopy. We resolve all these features using a Heisenberg-Kondo lattice model for EuB6, solved using exact diagonalisation based Langevin dynamics. Over a temperature window ∼0.7Tc−1.5Tc we observe electronic and magnetic textures with the correct spatial and energy scale, and confirm an associated non-monotonic resistivity. We predict a distinctly `non Drude' optical conductivity in the polaronic phase, and propose a field-temperature phase diagram testable through spin resolved tunneling spectroscopy. We argue that the anomalous properties of EuB6, and magnetic polaron materials in general, occur due to a non monotonic change in spatial character of `near Fermi level' eigenstates with temperature, and the appearance of a weak pseudogap near Tc.
@article{arxiv.2408.03628,
title = {Tunneling maps, non-monotonic resistivity, and non Drude optics in EuB$_6$},
author = {Tanmoy Mondal and Pinaki Majumdar},
journal= {arXiv preprint arXiv:2408.03628},
year = {2024}
}