Temperature and magnetic field-dependent tunneling study of Bi2Sr2CaCu2Oy in the pseudogap state

The existence of Cooper pairs above T-c is a popular theory of pseudogap in cuprates. The influence of magnetic field on such Cooper pairs should be d rastic, although magnitude of the field required can be quite large. We hav e performed tunneling measurements in the ab-plane direction on underdoped Bi2Sr2CaCu2Oy (Bi2212) single crystals with T-c = 65 K for SIS junction for med with a low-temperature STM. The gap value Delta was found to be 35 meV from low-temperature tunneling spectra. The gap stays at this value up to T -c and it becomes more smeared near T-c, but exists at least up to 150 K. T he spectra near 100 K were studied as a function of the magnetic field and no change in the gap features was observed up to 1.1T. (C) 2000 Elsevier Sc ience B.V. All rights reserved.