Tunable RKKY interaction in 30° twisted bilayer graphene

Abstract

By means of the Lanczos method, we study the Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction in 30° twisted bilayer graphene (TBG). We find that the RKKY interaction in 30° TBG is identical to the counterpart in monolayer graphene, i.e., it conforms with the R⁻³ decay rate and Saremi's rule holds. Then we study the RKKY interaction mediated by the carriers of the biased 30° TBG as well as the conduction electrons of the doped system. This RKKY interaction oscillates between ferromagnetic (FM) and antiferromagnetic (AFM) as the distance R between two magnetic impurities increases, and a long-range behavior of the R⁻² decay rate is established. Moreover, we also find that the strength and sign of the RKKY interaction in the 30° TBG can be readily controlled by altering the gate voltage or carrier doping.