Gate-Tunable Renormalization of Spin-Correlated Flat-Band States and Bandgap in a 2D Magnetic Insulator

Pin Lyu, Joachim Sødequist, Xiaoyu Sheng, Zhizhan Qiu, Anton Tadich, Qile Li, Mark T. Edmonds, Meng Zhao, Jesús Redondo, Martin Švec, Peng Song, Thomas Olsen*, Jiong Lu*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review


Emergent quantum phenomena in two-dimensional van der Waal (vdW) magnets are largely governed by the interplay between exchange and Coulomb interactions. The ability to precisely tune the Coulomb interaction enables the control of spin-correlated flat-band states, band gap, and unconventional magnetism in such strongly correlated materials. Here, we demonstrate a gate-tunable renormalization of spin-correlated flat-band states and bandgap in magnetic chromium tribromide (CrBr3) monolayers grown on graphene. Our gate-dependent scanning tunneling spectroscopy (STS) studies reveal that the interflat-band spacing and bandgap of CrBr3 can be continuously tuned by 120 and 240 meV, respectively, via electrostatic injection of carriers into the hybrid CrBr3/graphene system. This can be attributed to the self-screening of CrBr3 arising from the gate-induced carriers injected into CrBr3, which dominates over the weakened remote screening of the graphene substrate due to the decreased carrier density in graphene. Precise tuning of the spin-correlated flat-band states and bandgap in 2D magnets via electrostatic modulation of Coulomb interactions not only provides effective strategies for optimizing the spin transport channels but also may exert a crucial influence on the exchange energy and spin-wave gap, which could raise the critical temperature for magnetic order.

Original languageEnglish
JournalACS Nano
Issue number16
Pages (from-to)15441-15448
Publication statusPublished - 2023


  • 2D magnetic insulator
  • Band renormalization
  • Flat band
  • Gate-tunable device
  • STM


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