title: Electron tunneling spectroscopy of SmB6 studied by in situ nano-break-junction method.
abstract: Tunneling spectra of intermediate-valence semiconductor SmB6 are reported for in-situ break junctions, being able to make nano-scale planar tunnel junctions. The electron tunneling using break junction method is a powerful probe of the intrinsic energy gap. The investigated tunneling conductance dI/dV curves are mostly reproducible and symmetric with respect to the applied voltage. Two kinds of characteristic energy gaps are observed at 2E(d) = 20 mV and 2E(a) = 9 mV, which coincides well with those previously studied by point-contact spectroscopy and the activation energy fitted by our electrical resistivity data. The positions of the gap structures are independent of the zero-bias conductance, implying no additional voltage drop induced by the break junctions. The small anomaly at the activation energy 2E(a) indicates a relatively low density of in-gap states. Furthermore, the results of magnetic properties reveal the ratio of Sm2+:Sm3+ = 3.7:6.3 and the antiferromagnetic nature at high temperature.
authors: Department of Physics, Sogang University, Seoul 121-742, Korea.
authors: Hyun-Won
authors: HW
authors: Lee
authors: Kyujoon
authors: K
authors: Lee
authors: Seongmin
authors: S
authors: Choo
authors: Nahyun
authors: N
authors: Jo
authors: Myung-Hwa
authors: MH
authors: Jung