Although transition-metal nitrides have been widely applied for several decades, experimental investigations of their high-resolution electronic band structures are rare due to the lack of high-quality single-crystalline samples. Here, we report on the first momentum-resolved electronic band structures of titanium nitride (TiN) films, a remarkable nitride superconductor. The measurements of crystal structures and electrical transport properties confirmed the high quality of these films. More importantly, with a combination of high-resolution angle-resolved photoelectron spectroscopy and the first-principles calculations, the extracted Coulomb interaction strength of TiN films can be as large as 8.5 eV, whereas resonant photoemission spectroscopy yields a value of 6.26 eV. These large values of Coulomb interaction strength indicate that superconducting TiN is a strongly correlated system. Our results uncover the unexpected electronic correlations in transition-metal nitrides, potentially providing a perspective not only to understand their emergent quantum states but also to develop their applications in quantum devices.
@article{arxiv.2405.18150,
title = {Momentum-resolved electronic structures and strong electronic correlations in graphene-like nitride superconductors},
author = {Jiachang Bi and Yu Lin and Qinghua Zhang and Zhanfeng Liu and Ziyun Zhang and Ruyi Zhang and Xiong Yao and Guoxin Chen and Haigang Liu and Yaobo Huang and Yuanhe Sun and Hui Zhang and Zhe Sun and Shaozhu Xiao and Yanwei Cao},
journal= {arXiv preprint arXiv:2405.18150},
year = {2024}
}