Semiconducting gap of Nd1.85Ce0.15CuO4 revealed by break-junction tunnelling spectroscopy

Abstract

The quasiparticle energy spectrum of the semiconducting Nd 1.85Ce0.15CuO4 was probed by a break-junction technique. The tunnelling conductance exhibits well-defined gap-edge peaks at 4 K with peak-to-peak bias separations 2-2.8 eV, showing the V-shaped gap feature. The gap value 2Δ (4K) 1-1.4 eV is inferred in view of the very break-junction nature. As temperature, T, increases, the gap gradually disappears to merge with the background at T ∼ 200 K. Possible origins of the gap are discussed on the basis of the break-junction and complementary data obtained using scanning-tunnelling spectroscopy. © 2009 IOP Publishing Ltd.