Geometric frustration of particle motion in a kagome lattice causes the single-particle band structure to have a flat $s$-orbital band. We probe this band structure by placing a Bose-Einstein condensate into excited Bloch states of an optical kagome lattice, and then measuring the group velocity through the atomic momentum distribution. We find that interactions renormalize the band structure, greatly increasing the dispersion of the third band, which is nearly non-dispersing the single-particle treatment. Calculations based on the lattice Gross-Pitaevskii equation indicate that band structure renormalization is caused by the distortion of the overall lattice potential away from the kagome geometry by interactions.

中文翻译：

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光学 Kagome 晶格平带中玻色子的相互作用增强群速度

kagome 晶格中粒子运动的几何挫折导致单粒子带结构具有平坦$秒$-轨道带。我们通过将 Bose-Einstein 凝聚体置于光学 kagome 晶格的激发布洛赫态中，然后通过原子动量分布测量群速度来探测这种能带结构。我们发现相互作用使带结构重新归一化，大大增加了第三带的色散，这几乎是非分散的单粒子处理。基于晶格 Gross-Pitaevskii 方程的计算表明，能带结构重整化是由相互作用导致的整体晶格势远离 kagome 几何结构的畸变引起的。