Physics Colloquium - Electrons behaving badly: metallic properties at high magnetic fields in wide band-gap insulators

Presented by: John Singleton, National High Magnetic Field Laboratory, Los Alamos National Laboratory Abstract: From an early age, we are taught that metals are good conductors of electricity and heat but that insulators are not. At High School we learn that metals contain vast numbers of charged electrons that are free to move and carry heat and current, whereas insulators do not. At University, we find out that electrons are fermions, and perhaps comprehend Fermi-Dirac statistics, leading to the well-known definition that “a metal is a solid with a Fermi surface”. The Fermi surface is the constant-energy surface which at zero temperature separates the occupied electron states from the empty in momentum space; if we know the size and shape of a metal’s Fermi surface, we understand how its free electrons behave and hence can account for almost all of its electrical, thermal and magnetic properties. Over the past decade, this comforting picture has been upset by experiments on various m...