Seminars Archive

Metal-insulator transition in Ni compounds: some more surprises

Abstract
Metal-insulator transition is arguably one of the most outstanding problems of condensed matter physics. An unusual transition in the electrical resistivity of nickel monosulphide (NiS) has been the centre of many discussions and controversies for more than three decades, particularly in relation to the nature of the transition. We show that with the use of extremely high resolution photoemission studies, it is possible to understand this transition as a metal to unusual metal transition in contrast to a metal-to-insulator transition as previously believed. On the other hand, our recent photoemission study establishes for the first time a metal-insulator transition at the surface of a well-known insulating system, namely nickel disulphide, NiS2. I shall discuss these new results in the context of the previous knowledge and theoretical implications of these findings.