2022/06/29 by H. X. Zhang, Zhang, H. X., Y. X. Gao +3
Physics and Astronomy · Materials Science · #Theoretical and Computational Physics #Advanced Thermodynamics and Statistical Mechanics #Graphene research and applications
paper · pdf · doi:10.48550/arxiv.2206.14432
Ferromagnetism emerges when the Moire superlattice formed by stacking two graphene monolayers in a magic twist angle are filled with integer number electrons. This work investigates the ferromagnetism based on the Ising models for a triangular lattice at one-quarter filling, a square lattice at half filling and a Kagome lattice at three-quarters filling of electrons. The temperature dependent heat capacity, magnetic susceptibility, energy and magnetization curves are calculated at zero magnetic field with a Monte Carlo method, leading to derive the phase transition temperatures, Tc=0.76, 1.33 and 4.75 K, respectively. Magnetization curves at finite magnetic field show strong hysteresis at temperature below 0.5 K for all the fillings considered, indicating the ferromagnetism of the system; the results are in agreement with experimental observations.