论文标题
Fullerenes上的量子二聚体模型:共振,疤痕和限制
Quantum dimer model on fullerenes: resonance, scarring and confinement
论文作者
论文摘要
在有机化学中发现了最早的量子叠加实例 - 在$π$键的多种布置中“共振”的分子中。小分子(例如苯)在一些键排列之间产生共鸣。相反,在宏观晶格上延伸的大型系统可能会在大量配置之间产生共鸣。这类似于安德森(Anderson)共鸣键(RVB)图片所描述的量子自旋液体。在本文中,我们研究了一些大分子的中间情况,即C $ _ {20} $和C $ _ {60} $ fullerenes。我们在量子二聚体模型方面构建了一个最小的描述,从而允许局部共振过程和近距离$π$ bonds之间的排斥。这使我们能够以C $ _ {60} $形成5828二聚体盖的叠加来表征地面 - 例如。尽管有大量的二聚体覆盖物,但基态显示出强二聚体相关性。除了基态之外,C $ _ {60} $的全频谱显示出许多有趣的功能。它的希尔伯特空间是双方的,导致光谱反射对称性。它具有大量受保护的零能量状态。此外,频谱包含许多类似疤痕的状态,对应于局部二聚体重态性动力学。 QDM中的共振动力学可以在缺陷的行为中表现出来,通过有效的有吸引力的相互作用具有可能结合的缺陷。为了测试这个概念,我们在所有可能的分离中介绍了一对空缺。当空位彼此最接近时,共振能量达到了最低值。这表明单体的限制,尽管在有限的集群中。我们讨论定性图片,以了解富勒烯中的键合,并与量子化学的结果建立联系。
The earliest known examples of quantum superposition were found in organic chemistry -- in molecules that `resonate' among multiple arrangements of $π$-bonds. Small molecules such as benzene resonate among a few bond arrangements. In contrast, a large system that stretches over a macroscopic lattice may resonate among an extensive number of configurations. This is analogous to a quantum spin liquid as described by Anderson's resonating valence bond (RVB) picture. In this article, we study the intermediate case of somewhat large molecules, the C$_{20}$ and C$_{60}$ fullerenes. We build a minimal description in terms of quantum dimer models, allowing for local resonance processes and repulsion between proximate $π$-bonds. This allows us to characterize ground-states, e.g., with C$_{60}$ forming a superposition of 5828 dimer covers. Despite the large number of contributing dimer covers, the ground state shows strong dimer-dimer correlations. Going beyond the ground state, the full spectrum of C$_{60}$ shows many interesting features. Its Hilbert space is bipartite, leading to spectral reflection symmetry. It has a large number of protected zero-energy states. In addition, the spectrum contains many scar-like states, corresponding to localized dimer-rearrangement-dynamics. Resonance dynamics in QDMs can manifest in the behaviour of defects, potentially binding defects via an effective attractive interaction. To test this notion, we introduce pairs of vacancies at all possible separations. Resonance energy reaches its lowest value when the vacancies are closest to one another. This suggests confinement of monomers, albeit within a finite cluster. We discuss qualitative pictures for understanding bonding in fullerenes and draw connections with results from quantum chemistry.