National Synchrotron Light Source Seminar

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 phase 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 one-dimensional character of the stripe phase appears to be 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 by neutron elastic scattering, we argue that the PG phase may not be the stripe state but more resembles the checkerboard state seen by the STM/STS. A possible scenario of the local checkerboard states of the anti-nodal carriers interacting with the nodal p-metal leading to a two-component superconductivity is discussed.