Monolayer 1T-NbSe2 as a 2D-correlated magnetic insulator

Liu, Mengke
Leveillee, Joshua
Lu, Shuangzan
Yu, Jia
Kim, Hyunsue
Tian, Cheng
Shi, Youguo
Lai, Keji
Zhang, Chendong
Giustino, Feliciano
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American Association for the Advancement of Science

Monolayer group V transition metal dichalcogenides in their 1T phase have recently emerged as a platform to investigate rich phases of matter, such as spin liquid and ferromagnetism, resulting from strong electron correla- tions. Newly emerging 1T-NbSe2 has inspired theoretical investigations predicting collective phenomena such as charge transfer gap and ferromagnetism in two dimensions; however, the experimental evidence is still lacking. Here, by controlling the molecular beam epitaxy growth parameters, we demonstrate the successful growth of high-quality single-phase 1T-NbSe2. By combining scanning tunneling microscopy/spectroscopy and ab initio calculations, we show that this system is a charge transfer insulator with the upper Hubbard band located above the valence band maximum. To demonstrate the electron correlation resulted magnetic property, we create a vertical 1T/2H NbSe2 heterostructure, and we find unambiguous evidence of exchange interactions between the localized magnetic moments in 1T phase and the metallic/superconducting phase exemplified by Kondo reso- nances and Yu-Shiba-Rusinov–like bound states.

Mengke Liu et al. ,Monolayer 1T-NbSe2 as a 2D-correlated magnetic insulator.Sci. Adv.7,eabi6339(2021).DOI:10.1126/sciadv.abi6339