Joint-Institute of Neutron Sciences, Department of Materials Sciences and Engineering, and Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, and Oak Ridge National Laboratory, Oak Ridge, TN.
The exact nature of a transition from a doped Mott-Hubbard insulator to a Fermi-liquid metal is not well understood and is highly controversial. The pseudo-gap (PG) phase appears as an intermediate state in this transition, but again the nature of this phase is hotly debated. Many assume that the dynamic spin-charge stripe state is the underlying state of the PG phase, but the strongly one-dimensional character of the stripe phase is inconsistent with the highly two-dimensional nature of the electronic state, as revealed by the ARPES measurement. In this talk I argue that the paramagnetic state of the t-J model is different from the Fermi-liquid state, and a transition from a doped Mott-Hubbard d-band insulator to a Fermi-liquid p-band metal in the cuprate is a sharp transition, but is masked by disorder and the intermediate PG phase. Based upon the recent data on the phonon dispersion by inelastic neutron scattering and the short-range ordering peak newly discovered by neutron elastic scattering, we argue that the PG phase is not the stripe state but is a checkerboard state as seen by the STM/STS. A possible scenario of the local checkerboard states of the anti-nodal d-carriers interacting with the nodal p-metal leading to a two-component superconductivity is discussed.
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