High energy secondary peak structure in tunneling spectra (hump) as possible magnetic pseudogap

It is demonstrated that tunneling spectra in various high T-c cuprates disp lay generic features. The principal conductance peaks in superconductor-ins ulator-normal metal (SIN) junctions indicate the superconducting gap in the density of states (DOS). Higher energy features include a dip and hump str ucture with a strength that is asymmetric in bias voltage. The dip and hump features follow the doping trends of the superconducting gap, Delta, with a rough scaling as similar to2 Delta and similar to3 Delta respectively. Tu nneling spectra in underdoped Bi2Sr2CaCu2O8+delta display a more pronounced hump feature suggestive of a second gap in the DOS. It is observed that th e hump feature in the tunneling density of states is consistent with other experimental observations of the so-called high energy pseudogap which may have magnetic origins.