High-field interlayer tunnelling transport in layered cuprates: Uncovering the pseudogap state

In high temperature (high T _c ) cuprate superconductors the gap in the electronic density of states is not fully filled at T _c ; it evolves into a partial (pseudo)gap that survives way beyond T _c , challenging the conventional views. We have investigated the pseudogap phenomenon in the field-temperature (H-T) diagram of Bi₂Sr₂CaCu₂O_{8 + y} over a wide range of hole doping (). Using interlayer tunneling transport in magnetic fields up to 60 T to probe the density-of states (DOS) depletion at low excitation energies we mapped the pseudogap closing field H _pg . We found that H _pg and the pseudogap onset temperature T ^* are related via a Zeeman relation , irrespective of whether the magnetic field is applied along the c-axis or parallel to CuO₂ planes. In contrast to large anisotropy of the superconducting state, the field anisotropy of H _pg is due solely to the g-factor. Our findings indicate that the pseudogap is of singlet-spin origin, consistent with models based on doped Mott insulator.Received: 2 February 2004, Published online: 10 August 2004PACS: 74.25.Dw Superconductivity phase diagrams - 74.25.Fy Transport properties (electric and thermal conductivity, thermoelectric effects, etc.) - 74.72.Hs Bi-based cuprates