Anomalous properties in high-Tc cuprates due to inhomogeneous electronic states

最近在Bi2Sr2CaCu2O&lt；8+δ&gt；(BSCCO)中的扫描隧道显微镜和S的实验揭示了纳米尺度的不均匀性的存在，即两个不同区域的相对较小和较大间隙的斑块图案。这种不均匀性最显著的特征是：(1)大禁带区的伪隙类相谱，(2)小禁带区和大禁带区的空间均匀亚能隙谱，以及(3)出现单向长程电荷密度有序。结果表明，在铜酸盐中不可避免地引入离面无序来掺杂载流子，这是造成不均匀和带隙结构的主要原因。这种不均一性本身就引起了人们对高温物理的浓厚兴趣。此外，我们预计，对非均质性的观察可能有助于揭示这一领域中尚未解决的问题，对于这些问题，迄今为止甚至没有基于同质理论模型的定性理论解释。在这些背景的推动下，我们在Bogoliubov-de Gennes理论的基础上，基于扩展的Gutzwiter近似，研究了二维t-t‘-t“-J模型中的空间调制d波超导态。当系统空穴掺杂率约为12.5%时，我们找到了完全自洽的解，当系统空穴掺杂率约为12.5%时，磁畴壁被4个晶格间距隔开，而当空穴掺杂率约为15%时，磁畴壁的配对振幅Δ消失，晶格间距为5。相邻的超导磁区处于反相模式，即它们之间的相对相位差为π。由于凝聚能的损失，Δ=0域壁包含了可移动空穴的集中。我们还发现，在具有反相超导磁区结构的这些态中，在局域态密度的d波隙能量处的超导相干峰被强烈地抑制。

Recent STM/S experiments in Bi_2Sr_2CaCu_2O_<8+δ> (BSCCO) have revealed the existence of nanoscale inhomogeneities, that is, a pattern of patches of two different regions with relatively small and large gap. The most prominent features of the inhomogeneities are (i) the pseudogap phase-like spectra in the large gap regions, (ii) spatially homogeneous subgap spectra both in the small and large gap regions, and (iii) appearance of the unidirectional long-range charge density order. It is suggested that out-of-plane disorder, which is inevitably introduced into cuprates to dope charge carriers, is responsible for the inhomogeneity and the gap structures. The inhomogeneity itself generates intense interest in high-Tc, physics. Moreover, we expect that observations of inhomogeneity may help reveal unsolved problems in this field for which not even a qualitative theoretical explanation is so far available based on homogeneous theoretical models. Therefore, it is important to investigate the inhomogeneity, especially from the viewpoint of the nature of the large gap region.Motivated by these backgrounds, we study spatially modulated d-wave superconducting states in the two-dimensional t-t'-t"-J model within the Bogoliubov-de Gennes theory based on an extended Gutzwiller approximation. We find fully self-consistent solutions involving domain walls with vanishing pairing amplitudes Δ separated by four lattice spacing when the system is about 12.5% hole doping, while 5 at about 15%. The adjacent superconducting domains are in the anti-phase patterns, that is, the relative phase difference between them is π. The Δ=0 domain walls involve concentration of mobile holes due to the loss of the condensation energy. We also find that the superconducting coherence peaks at the energy of the d-wave gap in the local densities of states are strongly suppressed in these states with anti-phase superconducting domain structures.