Gate-Tunable Renormalization of Spin-Correlated Flat-Band States and Bandgap in a 2D Magnetic Insulator
Abstract
Emergentquantum phenomena in two-dimensional van der Waal (vdW)magnets are largely governed by the interplay between exchange andCoulomb interactions. The ability to precisely tune the Coulomb interactionenables 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-correlatedflat-band states and bandgap in magnetic chromium tribromide (CrBr3) monolayers grown on graphene.
Our gate-dependent scanningtunneling spectroscopy (STS) studies reveal that the interflat-bandspacing and bandgap of CrBr3 can be continuously tunedby 120 and 240 meV, respectively, via electrostaticinjection of carriers into the hybrid CrBr3/graphene system.This can be attributed to the self-screening of CrBr3 arisingfrom the gate-induced carriers injected into CrBr3, whichdominates over the weakened remote screening of the graphene substratedue to the decreased carrier density in graphene. Precise tuning ofthe spin-correlated flat-band states and bandgap in 2D magnets via electrostatic modulation of Coulomb interactions notonly provides effective strategies for optimizing the spin transportchannels but also may exert a crucial influence on the exchange energyand spin-wave gap, which could raise the critical temperature formagnetic order.