The first evidence for CDW transport in inorganic linear chain compounds, such as transition metal trichalcogenides, was reported in 1976 by Monceau et al., who observed enhanced electrical conduction at increased electric fields in NbSe 3. The nonlinear contribution to the electrical conductivity σ vs. field E was fit to a Landau-Zener tunneling characteristic ~ exp[- E 0 / E ] (see Landau–Zener formula), but it was soon realized that the characteristic Zener field E 0 was far too small to represent Zener tunneling of normal electrons across the Peierls gap. Subsequent experiments showed a sharp threshold electric field, as well as peaks in the noise spectrum (narrow band noise) whose fundamental frequency scales with the CDW current. These and other experiments (e.g.,) confirm that the CDW collectively carries an electric current in a jerky fashion above the threshold field.