Field-enhanced diamagnetism in the pseudogap state of the cuprate Bi2Sr2CaCu2O8+Î superconductor in an intense magnetic field

In hole-doped cuprates, Nernst experiments imply that the superconducting state is destroyed by spontaneous creation of vortices which destroy phase coherence. Using torque magnetometry on Bi2Sr2CaCu2O8+Î, we uncover a field-enhanced diamagnetic signal M above the transition temperature Tc that increases with applied field to 32Â Tesla and scales just like the Nernst signal. The magnetization results above Tc distinguish M from conventional amplitude fluctuations and strongly support the vortex scenario for the loss of phase coherence at Tc.