PSEUDOGAP IN CUPRATE SUPERCONDUCTORS: EXPLORING SCALING AND QUANTUM CRITICAL END POINT

Abstract

We explore extremely overdoped regime in the phase diagram of cuprate superconductors. Interlayer tunneling transport measurements under high magnetic fields are employed to detect the field dependence of low-energy density of states (DOS) in hole-doped (BSCCO and TBCO), and electron-doped (SCCO) cuprates. We find a strong doping dependence of the pseudogap closing field whose Zeeman energy universally scales with the pseudogap onset temperature, indicating a preeminent role of spin-singlet correlations in forming the pseudogap regardless of the doping type. Excess dissipation due to the pseudogap is found to follow a 'universal' correlation with the pseudogap closing field. The pseudogap features appear absent in the extremely overdoped TBCO, pointing to a possible quantum critical point very near the edge of the superconducting 'dome'.