Does filling-dependent band renormalization aid pairing in twisted bilayer graphene?
Does filling-dependent band renormalization aid pairing in twisted bilayer graphene?
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DOI：
10.1038/s41535-021-00379-6
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发表时间：
2021-02
影响因子：
5.7
通讯作者：
C. Lewandowski;S. Nadj-Perge;D. Chowdhury
中科院分区：
文献类型：
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作者：
C. Lewandowski;S. Nadj-Perge;D. Chowdhury
魔角扭曲双层石墨烯（MATBG）表现出一系列多体现象，这些现象与狭窄且隔离良好的电子带的出现密切相关。负责复杂的实验现象学的微观成分包括电子-电子（声子）相互作用和与窄带相关的非平凡布洛赫波函数。最近的实验的启发，我们专注于两个独立的量，库仑相互作用驱动的带重正化，即状态密度和最小的空间范围与Wannier功能，大大修改。首先，我们表明，填充依赖增强的状态密度，所造成的频带平坦化，结合声子介导的吸引力，由于电子-声子umklapp过程，增加了超导配对的趋势，在一个范围内的角度周围的魔角。其次，我们证明了与Wannier函数相关的最小空间范围，这有助于增加超导相刚度，也发展了一个非平凡的增强由于相互作用引起的重整化的布洛赫波函数。虽然我们的超导性（SC）模型假设弱的电子-声子耦合，并没有考虑许多可能的相关效应，它只是解释了实验观察到的SC的鲁棒性在宽范围的角度发生在相关范围的填充。
Magic-angle twisted bilayer graphene (MATBG) exhibits a panoply of many-body phenomena that are intimately tied to the appearance of narrow and well-isolated electronic bands. The microscopic ingredients that are responsible for the complex experimental phenomenology include electron–electron (phonon) interactions and nontrivial Bloch wavefunctions associated with the narrow bands. Inspired by recent experiments, we focus on two independent quantities that are considerably modified by Coulomb interaction-driven band renormalization, namely the density of states and the minimal spatial extent associated with the Wannier functions. First, we show that a filling-dependent enhancement of the density of states, caused by band flattening, in combination with phonon-mediated attraction due to electron-phonon umklapp processes, increases the tendency towards superconducting pairing in a range of angles around magic-angle. Second, we demonstrate that the minimal spatial extent associated with the Wannier functions, which contributes towards increasing the superconducting phase stiffness, also develops a nontrivial enhancement due to the interaction-induced renormalization of the Bloch wavefunctions. While our modeling of superconductivity (SC) assumes a weak electron-phonon coupling and does not consider many of the likely relevant correlation effects, it explains simply the experimentally observed robustness of SC in the wide range of angles that occurs in the relevant range of fillings.