| Budget Amount *help |
¥1,680,000 (Direct Cost: ¥1,500,000、Indirect Cost: ¥180,000)
Fiscal Year 2007: ¥780,000 (Direct Cost: ¥600,000、Indirect Cost: ¥180,000)
Fiscal Year 2006: ¥900,000 (Direct Cost: ¥900,000)
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| Research Abstract |
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.
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