AI 中文总结
本文采用连续场动量空间量子蒙特卡洛方法，发现扭曲双层石墨烯低温正常态存在狄拉克激子，其光谱可通过扭转角和层间跃迁强度调控，为强关联拓扑带多体激发研究提供了新方向。
AI 中文摘要
确定电荷载流子的性质是强关联电子系统研究的基本目标。本文采用连续场动量空间量子蒙特卡洛方法，揭示扭曲双层石墨烯有限温度正常态中存在奇异的“狄拉克激子”激发。基态是具有~20 meV带隙类电子激发的对称性破缺绝缘体，研究表明，远低于相互作用尺度的~3 meV低温可驱动系统进入强涨落的对称正常态。该正常态包含由两个电子和一个空穴组成的三粒子束缚态构成的无隙激发，在零动量无隙点处与高能电子完全正交。这些狄拉克激子具有由重组分构成却可任意轻的显著特性，其光谱可通过改变扭转角和层间跃迁强度轻松调控。本文的无偏量子多体计算阐明了投影关联平带环境下的狄拉克激子，为进一步研究朗道能级之外强关联拓扑带中的多体激发开辟了道路。
英文摘要
Determining the nature of charge carriers is a fundamental goal in the study of strongly correlated electron systems. Here, we employ the continuous-field momentum-space quantum Monte Carlo method to reveal exotic "Dirac trion" excitations in the finite-temperature normal state of twisted bilayer graphene. While the ground state is a symmetry-breaking insulator with gapped ($\sim$ 20 meV) electron-like excitations, we show that a small temperature ($\sim$ 3 meV), well below the interaction scale, drives the system into a strongly fluctuating symmetric normal state. We demonstrate that this normal state hosts gapless excitations consisting of three-particle bound states, two electrons and one hole, that are exactly orthogonal to the higher-energy electrons at the zero-momentum gapless point. These Dirac trions have the remarkable property of being arbitrarily light despite being composed of heavy constituents, and their spectra can be easily tuned by varying the twist angle and interlayer hopping strength. Our unbiased quantum many-body computation sheds light on the Dirac trions in a projected correlated flat-band setting and opens the door for further investigation of many-body excitations in strongly correlated topological bands beyond Landau levels.
Comments8 pages, 4 figures in the main text, 5 pages, 1 figure in the Supplemental Material
