Figure 100: Plot of the band gap atk = 2 πaOne example for a Peierls transition is shown in fig. 101. Due to two different types of bonds (single
and double) the lattice is dimerized and as a result a Peierls transition can be observed.
Figure 101: Structure of polyacetylene. The lattice gets dimerized because of the single and double
bonds. Furthermore Peierls transition is possible
Another example for a Peierls transition would beNbSe 3. This certain crystal is a very good conductor
in onedirection and because of the Peierls transition it gets an insulator when the system cools down.
If the material is an insulator the electron density forms a wave and as a result, dimerized regions can
be observed. This wave starts to slide if an electric field affects on the material. Fig. 102 shows the
current versus voltage for such a material at low temperatures. At a particular point (high electric
field) the current starts to increase, that’s the point where the electron density wave starts to slide.