论文标题
拓扑平坦带中的多体超导性
Many-Body Superconductivity in Topological Flat Bands
论文作者
论文摘要
在平坦的频带超导体中，骨气激发可以分散，而未配对的电子是不动的。为了研究这种强烈的相互作用的系统，我们在所有空间组中构建了一个具有精确的ETA配对基态的多频段哈伯德模型的家族。我们通过分析计算他们的多体激发，发现库珀对结合的状态和密度激发服从了一种有效的单粒子汉密尔顿，以非相互作用的波形作用。这些结合状态具有独特的零能激发，其二次分散剂由最小量子度量确定。其余结合状态频谱通过拓扑量子化学分类，我们用来识别与Weyl节点，较高的角动量配对和脆弱拓扑结构的库珀对。我们还添加了电子动能作为扰动，以表明最强的配对发生在一半填充，而不是最高密度。这在精神上与在扭曲的双层石墨烯中观察到的超导性相似。
In a flat band superconductor, bosonic excitations can disperse while unpaired electrons are immobile. To study this strongly interacting system, we construct a family of multi-band Hubbard models with exact eta-pairing ground states in all space groups. We analytically compute their many-body excitations and find that the Cooper pair bound states and density excitations obey an effective single-particle Hamiltonian written in terms of the non-interacting wavefunctions. These bound states possess a unique zero-energy excitation whose quadratic dispersion is determined by the minimal quantum metric. The rest of the bound state spectrum is classified by topological quantum chemistry, which we use to identify Cooper pairs with Weyl nodes, higher angular momentum pairing, and fragile topology. We also add electron kinetic energy as a perturbation to show that the strongest pairing occurs at half filling and not at the highest density of states. This is similar in spirit to the superconductivity observed in twisted bilayer graphene.
