论文标题
在扭曲的双层石墨烯模型中
Quantum Monte Carlo sign bounds, topological Mott insulator and thermodynamic transitions in twisted bilayer graphene model
论文作者
论文摘要
我们表明，对于魔法扭曲的双层石墨烯（TBG），尽管量子蒙特卡洛（QMC）模拟遇到了符号问题，但远离电荷中立性，计算复杂性在某些整数填充物中最多是多项式的。对于甚至整数填充物，即使在库仑排斥的基础上引入了额外的valley相互作用，这种多项式复杂性也可以生存。该观察结果使我们能够模拟魔法扭曲的双层石墨烯并获得准确的相图和动力学特性。在手性极限并填充$ν= 1 $的情况下，模拟显示了将金属状态分离的热力学过渡和$ C = 1 $相关的Chern绝缘子 - 拓扑莫特绝缘子（TMI），以及在过渡温度上方略微上方的伪群。 TMI的基态激发光谱表现出自旋valley U（4）Goldstone Mode和时间逆转恢复的激发隙，而激发差距小于单个粒子间隙。这些结果在质量上与零场的最新实验发现和$ν= 1 $填充$ h $ h $ bn非对齐的TBG一致。
We show that for magic-angle twisted bilayer graphene (TBG) away from charge neutrality, although quantum Monte Carlo (QMC) simulations suffer from the sign problem, the computational complexity is at most polynomial at certain integer fillings. For even integer fillings, this polynomial complexity survives even if an extra inter-valley attractive interaction is introduced, on top of Coulomb repulsions. This observation allows us to simulate magic-angle twisted bilayer graphene and to obtain accurate phase diagram and dynamical properties. At the chiral limit and filling $ν=1$, the simulations reveal a thermodynamic transition separating metallic state and a $C=1$ correlated Chern insulator -- topological Mott insulator (TMI) -- and the pseudogap spectrum slightly above the transition temperature. The ground state excitation spectra of the TMI exhibit a spin-valley U(4) Goldstone mode and a time reversal restoring excitonic gap smaller than the single particle gap. These results are qualitatively consistent with the recent experimental findings at zero-field and $ν=1$ filling in $h$-BN nonaligned TBG.
