On the spin origin of the pseudogap in high-T-c superconductors

We report on the magnetic field dependence of the pseudogap in Bi2Sr2CaCu2O 8+y obtained through measurements of the c-axis tunneling resistivity in fi elds up to 60 T that probes the low-energy density of states (DOS). A field that restores DOS to its ungapped state shows strikingly different tempera ture dependence from the characteristic fields of the superconducting state . We find that the pseudogap closing field and the pseudogap temperature ar e related through a simple Zeeman energy scaling. These findings indicate a predominant role of spins over the orbital effects in the formation of the pseudogap. (C) 2001 Elsevier Science B.V. All rights reserved.