The recent experimental realization of two-dimensional (2D) transition metal nitrides (TMNs, e.g., Mo5N6, {\delta}-MoN, and W5N6) opens new opportunities for exploring their fundamental physical properties at the two-dimensional limit. In this work, we propose a unified picture of transport phenomena in the nitrogen-rich 2D W5N6 and Mo5N6, and the stoichiometric 2D {\delta}-MoN based on several observations and first-principles calculations. Temperature coefficient of resistance (TCR) and magnetoresistance (MR) from Hall measurements consistently suggest disorder-induced transport mechanism at low temperatures (10-30 K). Notably, we observe a transition from metal to semimetal driven by the variation of nitrogen content in TMNs, supported by the suppressed density of states at the Fermi energy in nitrogen-rich TMNs (e.g. Mo5N6) from first-principle calculations. Carrier density calculations of bulk TMNs and 2D TMNs with -NH termination groups further reveal the switching of majority carrier type of Mo5N6 at reduced thickness, which is in great agreement with Hall measurement results. Our findings demonstrate that high nitrogen content in metallic molybdenum nitrides can induce the transition to a semimetallic phase at the 2D limit, shedding light on both the fundamental aspects of these materials and directions in future material design.
@article{arxiv.2603.24873,
title = {Suppression of Metallic Transport in Nitrogen-rich Two-Dimensional Transition Metal Nitrides},
author = {Hongze Gao and Da Zhou and Nguyen Tuan Hung and Chengdong Wang and Zifan Wang and Ruiqi Lu and Yuxuan Cosmi Lin and Jun Cao and Michael Geiwitz and Gabriel Natale and Kenneth S. Burch and Xiaofeng Qian and Riichiro Saito and Mauricio Terrone and Xi Ling},
journal= {arXiv preprint arXiv:2603.24873},
year = {2026}
}