AI 中文总结
本研究针对魔角螺旋三层石墨烯形成的超莫尔陈马赛克，通过中等磁场诱导谷选择性拓扑转变，在4.6K下实现了陈数C=-6的量子化霍尔电阻输运。
AI 中文摘要
魔角螺旋三层石墨烯——三层石墨烯以相同方向依次扭转约1.8°——弛豫为畴的马赛克结构，在零场下，这些畴携带相反的谷分辨陈数，其边界承载着无隙导电模式的网络。通过该网络的电荷输运对模式的连接和散射方式敏感，使得良好量子化的输运不太可能。与该预期相反，我们观察到在电荷中性处产生了场诱导的陈隙，其陈数C=-6；在该隙中，4.6K下的霍尔电阻被量子化至预期值-h/6e²的2%以内。我们利用霍夫施塔特（Hofstadter）和轨道塞曼（orbital Zeeman）计算解释该行为，计算表明中等磁场驱动谷选择性拓扑转变。在该转变之上，每个自旋谷味的占据态总陈数在相邻畴间变得相同，且畴壁模式可成为有隙的。尽管两种畴类型间的中心价带陈数仍存在差异，但观察到的量子化输运证实了全局隙的存在。
英文摘要
Magic-angle helical trilayer graphene---three graphene layers sequentially twisted in the same direction by $\sim1.8^\circ$---relaxes into a mosaic of domains that, at zero field, carry opposite valley-resolved Chern numbers, with boundaries hosting a network of gapless conducting modes. Charge transport through this network depends sensitively on how the modes connect and scatter, making well-quantized transport unlikely. Contrary to this expectation, we observe a field-induced Chern gap with Chern number $C=-6$ emanating from charge neutrality; in this gap, the Hall resistance is quantized to within $2\%$ of the expected value, $-h/6e^2$, at 4.6 K. We explain this behavior using both Hofstadter and orbital Zeeman calculations, which show that a moderate magnetic field drives a valley-selective topological transition. Above the transition, the total Chern number of the occupied states in each spin-valley flavor becomes identical across neighboring domains, and the domain-wall modes can become gapped. Though the central valence-band Chern numbers still differ between the two domain types, the observed quantized transport attests to a global gap.
Comments10+22 pages, 4+27 figures
