基于双轨道模型单层铜氧化物高温超导体的量子蒙特卡罗探究

Quantum Monte Carlo Study of the Single-Layered High-Tc Cuprates with a Two-Orbital Model

摘要: 基于描述单层铜氧化物高温超导体的双轨道模型(包含 和 轨道)，我们采用约束路径量子蒙特卡罗方法研究了La_2−x(Sr/Ba)_xCuO₄和HgBa₂CuO_4+x的超导特性。我们发现随着两个轨道间能量差ΔE的增加，d波配对关联函数被显著增强。该结果合理解释了HgBa₂CuO_4+x相比于La_2−x(Sr/Ba)_xCuO₄具有更高超导临界转变温度这一特性。由于两个超导体系中的自旋关联函数相似，因而形成库伯对的反铁磁自旋涨落不是导致与材料相关的超导特性的根源。进一步分析发现 轨道上的空穴浓度随着ΔE的增大而增加，使得有更多空穴参与配对的HgBa₂CuO_4+x具有更高的超导临界转变温度。我们的研究有助于理解单层铜氧化物高温超导体的超导特性。

Abstract: On the basis of a two-orbital model (including and orbitals), we perform a systematic study of the superconducting property in single-layered La_2−x(Sr/Ba)_xCuO₄ and HgBa₂CuO_4+x by using the constrained-path Monte Carlo method. We find that the d-wave pairing correlation is strongly enhanced with increasing the energy difference ΔE between and orbitals, which provides a reasonable explanation of higher superconducting critical temperature Tc in HgBa₂CuO_4+x than in La_2−x(Sr/Ba)_xCuO₄. The similar spin correlations in the La- and Hg-based systems suggest that antiferromagnetism is not responsible for material-dependent superconductivity. Further analysis indicates that the hole density on the orbital increases with increasing ΔE, leading to a higher Tc in the Hg-based system with larger ΔE. Our results are useful for understanding the superconducting property in single-layered high-Tc cuprates.