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

最近的STM/S实验表明，在Bi_2Sr_2CaCu_2O_（8+δ）（BSCCO）中存在纳米尺度的不均匀性，即由两个不同的区域组成的相对小的和相对大的间隙。的不均匀性的最突出的特点是：（i）在大的间隙区域的赝间隙相位的光谱，（ii）空间均匀的subgap光谱在小的和大的间隙区域，和（iii）外观的单向长程电荷密度顺序。这表明，面外无序，这是不可避免地引入到铜氧化物掺杂的电荷载流子，是负责的不均匀性和差距结构。这种不均匀性本身就引起了人们对高Tc物理的浓厚兴趣。此外，我们预计，观测的不均匀性可能有助于揭示未解决的问题，在这一领域，甚至没有一个定性的理论解释是迄今为止可用的基础上均匀的理论模型。基于这些背景，我们在Bogoliubov-de Gennes理论的基础上，基于扩展的Gutzwiller近似，研究了二维t-t '-t”-J模型中的空间调制d波超导态。当体系空穴掺杂量为12.5%时，我们发现了完全自洽的解，其中畴壁对振幅Δ为零，间距为四个晶格间距，而当体系空穴掺杂量为15%时，我们发现了完全自洽的解。相邻的超导畴呈反相分布，即它们之间的相对相位差为π。Δ=0畴壁由于凝聚能的损失而涉及移动的空穴的集中。我们还发现，超导相干峰的d-波隙的能量的局域态密度被强烈抑制在这些国家与反相超导畴结构。

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.