On the spin origin of the pseudogap in high-T_c superconductors

We report on the magnetic field dependence of the pseudogap in Bi2Sr2CaCu2O8+y obtained through measurements of the c-axis tunneling resistivity in fields 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 temperature dependence from the characteristic fields of the superconducting state. We find that the pseudogap closing field and the pseudogap temperature are 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. © 2001 Elsevier Science B.V. All rights reserved.