Magnetic correlations in single-layer NbSe2

By means of spin-resolved density functional theory calculations using both atomic orbitals and plane-wave basis codes, we study the electronic and magnetic ground state of single-layer NbSe2. We find that, for all the functionals considered, the most stable solution in this two-dimensional (2D) superconductor is the ferrimagnetic ground state with a magnetic moment of 1.09 μB at the Nb atoms and of 0.05 μB at the Se atoms pointing in the opposite direction. Our calculations show that the ferrimagnetic state precludes the development of charge density wave (CDW) order and their coexistence in the single-layer limit, unless graphene is considered as a substrate. The spin-resolved calculated density of states (DOS), a key fingerprint of the electronic and magnetic structure of a material, unambiguously reproduces the experimental DOS measured by scanning tunneling spectroscopy in single-layer NbSe2. Our work sets magnetism into play in this prototypical correlated 2D material, which is crucial to understand the formation mechanisms of 2D superconductivity and CDW order.
We are indebted to Spanish Ministry of Science and Innovation for financial support through Grant FIS2015-64886-C5-5-P and MAT2017-83553-P. MMU acknowledges support by the Spanish MINECO under Grant No. MAT2017-88377-C2-1-R and by the ERC Starting Grant LINKSPM (Grant 758558). EB acknowledges support from the Scientific and Technological Research Council of Turkey (TUBİTAK) under Grant No. 1059B141801387 and DSP from Spanish Ministry of Science and Innovation under Grant PID2019-107338RB-C66.