LiV2O4 is a spinel-structured compound that stands out as the first known 3d-electron system exhibiting typical heavy fermion behavior. A central question is how such strong mass renormalization emerges in the absence of f-electrons. In this work, we investigate the three-dimensional electronic structure of LiV2O4 thin films using angle-resolved photoemission spectroscopy (ARPES). We identify that an electron-like flat band is derived from a1g orbitals, along with a highly dispersive e'g band strongly coupled with phonons. The overall agreement with dynamical mean-field theory (DMFT) calculations highlights the essential role of inter-orbital Hund's coupling in reducing the a1g bandwidth to 25 meV, approaching a Mott state. Notably, we find that heavy-fermion behavior arises from additional renormalization at the a1g band near the Fermi level, likely driven by many-body interactions at energy scales down to a few meV and potentially linked to geometric frustration inherent to the spinel lattice. These results provide crucial insights into the origin of the heavy fermion behavior in 3d-electron systems.
@article{arxiv.2509.05237,
title = {Correlation-driven 3d Heavy Fermion behavior in LiV2O4},
author = {Min-Yi-Nan Lei and Z. H. Chen and H. T. Wang and Y. Fan and N. Guo and T. X. Jiang and Yanwei Cao and T. Zhang and Rui Peng and Haichao Xu},
journal= {arXiv preprint arXiv:2509.05237},
year = {2025}
}