AI 中文总结
研究平带超导体中，当平带与下带接触时，基于相互作用诱导能隙的BEC机制仍稳健高效，可形成轻质量束缚对，实现极高$T_c$。
AI 中文摘要
费米子的束缚玻色对形成及其随后的玻色-爱因斯坦（准）凝聚（BEC）是超导的基础机制。在低填充时，若平带与占据的下带间存在能隙，该机制可很好地描述平带超导。然而，当非相互作用的平带与下带接触时（如本文研究的原型吸引型Lieb晶格模型），预计会出现特别高的临界温度$T_c$，这与传统图像矛盾：虽然相互作用可能通过打开能隙保护束缚态，但没有小参数保证束缚态能量与该能隙或占据带激发的分离，导致对该对的命运不确定。基于受控精度的数值协议（我们证明其在这个根本非微扰问题中至关重要），我们表明由相互作用诱导能隙支撑的BEC机制通常是稳健且极其高效的：掺杂到平带中的费米子在该能隙内形成束缚对，具有异常轻的有效质量，从而实现极高的$T_c$。
英文摘要
The formation of bound bosonic pairs of fermions, followed by their Bose-Einstein (quasi) condensation (BEC), is a foundational mechanism of superconductivity. At low filling, flat-band superconductivity is well captured by this mechanism provided the flat band is separated from the occupied lower band by an energy gap. However, particularly high $T_c$ values are anticipated when the non-interacting flat and lower bands touch---as in the prototypical attractive Lieb-lattice model studied here---invalidating the conventional picture: while interactions might protect the bound state by opening a gap, no small parameter guarantees the separation of the bound-state energy from this gap or occupied-band excitations, leaving the pair's fate uncertain. Based on a controlled-precision numerical protocol---which we demonstrate to be essential in this fundamentally non-perturbative problem---we show that the BEC mechanism, underpinned by an interaction-induced gap, is generically robust and remarkably efficient: fermions doped into the flat band form bound pairs within this gap with an anomalously light effective mass, enabling an exceptionally high $T_c$.
Comments5 pages, 6 figures
