Charge-density-wave gaps of NbSe3 measured by point-contact spectroscopy in different crystallographic orientations -: art. no. 125117

We have measured the differential current-voltage (IV) characteristics of normal-metal (Au, Cu, In)-NbSe3 direct point contacts (without insulating barrier) formed along different crystallographic orientations. For all investigated directions, at low temperature we clearly observed two charge-density-wave gaps Delta(p1) and Delta(p2) as excess resistance singularities in the IV curves. The excess resistance is attributed to the reflection of injected carriers from the normal metal on the Peierls energy gap barriers. The analysis of these results demonstrates the two-dimensional character of the electronic spectrum in NbSe3 with a possible strong anisotropy of the energy gap in b-c plane.