四方哈伯德团簇中对角跃迁和近邻库仑相互作用的物理影响

Effect of Diagonal Hopping and Nearest-Neighbor Coulomb Interaction in Square Hubbard Clusters

摘要: 铜氧化物高温超导体中纳米尺度的电子态对理解这类材料的复杂物理特性和非常规超导机理具有重要的意义。本文采用数值精确对角化方法研究了纳米尺度四方哈伯德团簇中对角跃迁t'和近邻库仑相互作用V对电子对束缚能、自旋和电荷能隙及其对应跨越温度的物理影响。研究结果表明对角跃迁t'有效地扩展了电子配对、自旋和电荷配对的哈伯德U参数区间，升高了它们对应的跨越温度；与此相反，近邻库仑相互作用V显著地缩小了电子配对、自旋和电荷配对的哈伯德U参数区间，并降低了它们对应的跨越温度。当V与哈伯德U产生的有效电子吸引相互作用能量尺度相当时，在整个U值区间不能形成稳定的电子配对态。我们的研究结果说明t'有利于形成电子配对的超导态，而V将抑制超导态的形成。

Abstract: In the high-Tc cuprates, the nanoscale electronic state is important for understanding their com-plex physical properties and unconventional superconducting mechanism. In this work, numerical exact diagonalization method has been used to study the effect of diagonal hopping t' and nearest-neighbor Coulomb interaction V on the electron pair binding energy, spin and charge gaps and corresponding crossover temperatures in the square Hubbard clusters. The calculated results show that t' extends the regime of U in which electron, spin and charge pairings are formed, and corresponding crossover temperature increased. On the contrary, V exhibits opposite effects com- pared to t'. When V approaches to the energy scale of effective attraction induced by U, electron pairing is completely destroyed. Our findings demonstrate that t' can help the formation of superconducting state, while V will suppress the superconductivity.