Excitonic insulators are electronically-driven phases of matter characterized by the spontaneous condensation of electron-hole pairs. Here we show that La3Cd2As6 undergoes a transition at T0=278 K to a highly insulating state with no accompanying structural transition. We observe quasi-two-dimensional electrical transport and charge fluctuations consistent with an electronic transition enabled by enhanced Coulomb interactions. Density functional theory calculations are unable to replicate the insulating ground state. Our results support the opening of a gap by excitonic effects at T0, placing La3Cd2As6 as a rare example of a bulk excitonic insulator.
@article{arxiv.2506.09235,
title = {Putative excitonic insulating state in narrow-gap semiconductor La$_3$Cd$_2$As$_6$},
author = {Caitlin S. Kengle and Noah Schnitzer and Elizabeth A. Peterson and Chunyu Guo and Ling Zhang and Matthew S. Cook and Jian-Xin Zhu and Sean M. Thomas and Philip J. W. Moll and Filip Ronning and Priscila F. S. Rosa},
journal= {arXiv preprint arXiv:2506.09235},
year = {2025}
}