Termination-dependent electronic structure reconstruction in epitaxial EuTe4 thin films

Abstract

Layered EuTe4 has attracted considerable interest due to its intertwined charge density wave (CDW) phases and unconventional thermal hysteresis. While bulk EuTe4 has been extensively studied, its electronic structure in the thin-film limit remains largely unexplored. Here, we investigate epitaxial EuTe4 thin films and reveal a surface-induced electronic reconstruction absent in bulk crystals. Two distinct surface terminations are identified, and the TeI monolayer termination generates an additional M-shaped valence band derived from Te-pz orbitals. Despite this surface modification, Fermi surface nesting associated with CDW bands is preserved in the thin-film form. Moreover, a pronounced thermal hysteresis of the α band is observed in the temperature range of 9–150 K, in clear contrast to the 100–400 K hysteretic behavior reported in bulk EuTe4. Our results reveal the crucial role of surface termination in reshaping the electronic structure and hysteretic response of EuTe4, establishing thin films as a controllable platform for tuning interacting CDW phases and their hysteretic response.