The scaling theory of localization demonstrated that the disorder-induced M-I transition was a true phase transition with a well defined critical point.

The transitions from metallic to critical behavior and from critical to insulating behavior have been induced with a magnetic field, and from insulating to critical and then to metallic behavior with increasing external pressure.

In spite of the evidence for the disorder-induced M-I transition as inferred from the transport and optical measurements, the metallic state of conjugated polymers has been a subject of controversy.

Alan J. Heeger Quotes