Point-contact spectroscopy of quasi-1D conductors with CDW

Abstract
The nature of carrier reflection from a normal metal-Peierls conductor interface is clarifiecl by studying both the characteristics of direct point contacts Au-NbSe₃ (K_0.3MoO₃) oriental along the chains, and point contacts formed with an intermediate metallic layer sputtered onto the K_0.3MoO₃ crystals. In the Peierls state, for bias voltages eV smaller than the Peierls gap Δ_p, an excess differential resistance is observed for both experimental configuration. The dominant contribution to the excess resistance for injection along the chains is from normal reflection of carriers without changes in the sign of their charge and a momentum transfer 2p_F to the condencate of electron-hole pairs carried away from the interface. For Au-K_0.3MoO₃ contacts the character of nonlinearity and the observed asymmetric features of the IV characteristics indicate that a substantial shift of the chemical potential occurs near the boundary with the normal metal.