AI 中文总结
研究 kagome 晶格上零温吸引 Hubbard 模型，用辅助场量子蒙特卡罗模拟，发现 2/3 密度时特定临界吸引相互作用下有超流转变且无电荷序，1/3 填充时电荷序出现条件特殊，有范霍夫奇点密度时吸引相互作用也导致无电荷序超流。
AI 中文摘要
我们使用辅助场量子蒙特卡罗模拟，研究了 kagome 晶格上不同电子填充下的零温吸引 Hubbard 模型。在 2/3 密度时，低能物理受费米能处狄拉克点影响，我们发现临界吸引相互作用 \(U_c/t=-4.58(3)\) 时的超流转变，属于手征 XY 普适类。这种 U(1) 对称性破缺不伴随电荷序，即便相互作用强度很大。研究表明 1/3 填充时电荷序仅在远大于对应原费米子模型映射的相互作用强度时出现。对于在非相互作用态密度中有范霍夫奇点的密度，结果显示任何吸引相互作用都会导致超流性且无电荷序。
英文摘要
Using auxiliary-field quantum Monte Carlo simulations, we study the zero-temperature attractive Hubbard model on the kagome lattice at various relevant electronic fillings. The low-energy physics at $2/3$-density is influenced by the Dirac point at the Fermi energy, wherein we unveil a superfluid transition at a critical attractive interaction $U_c/t=-4.58(3)$, which belongs to the chiral-XY universality class. This U(1) symmetry-breaking is not accompanied by charge order, even for substantially large interaction strengths, in a regime where a description in terms of hardcore bosons becomes increasingly suitable. An investigation of the latter shows that charge ordering at $1/3$-filling only occurs at interaction strengths much larger than those corresponding to the mapping to the original fermionic model. Additionally, for densities exhibiting van Hove singularities in the non-interacting density of states, our results show that any attractive interaction gives rise to superfluidity, yet again without charge ordering, contrary to recent studies employing mean-field theory.
Comments10 pages, 7 figures
