Charge density wave gap formation of NbSe3 detected by electron tunneling

Tunneling spectra of NbSe3 between 77 K and room temperature have been meas ured carefully. A charge density wave (CDW) pseudogap exists up to a temper ature higher than similar to 260 K. While the gap parameter undergoes an ac celerated change between similar to 130 and similar to 160 K, the junction conductance at zero bias does not show any anomaly around T-1 = 145 K, the upper CDW transition temperature. Below the mean field transition temperatu re there are four regimes: a regime where a true CDW state exists, a regime where pinned and mobile CDW coexist, a regime of a pseudogap, and a regime where the CDW fluctuation can barely be detected by current measurements.