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arXiv · 2206.14432

Ferromagnetism in Magic-angle Twisted Bilayer Graphene: A Monte Carlo Study

H. X. Zhang·Y. X. Gao·Z. J. Ding
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Abstract

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, T_c=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.

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H. X. Zhang, Y. X. Gao, Z. J. Ding. 2022-06-29. Ferromagnetism in Magic-angle Twisted Bilayer Graphene: A Monte Carlo Study. https://arxiv.org/abs/2206.14432

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