Liquid MnTe: An example of a Mott-Hubbard liquid semiconductor

Abstract

A series of experiments performed in our laboratory have shown that liquid alloy systems of the form MTe (M is a transition metal other than Mn) combine salt-like structural order with a high electrical conductivity. This apparent contradiction can be resolved in terms of the Mott transition, that is to say, the d-bands associated with M are delocalized and are therefore able to contribute significantly to the conductivity. The situation for liquid MnTe is totally different. Here, the salt-like structural order is associated with a very low electrical conductivity because the splitting of the two sub-d-bands is sufficiently large to give a deep pseudogap in the density of states. Furthermore, since the splitting of the d-bands is an intra-atomic effect, the pseudogap should be essentially independent of temperature. We therefore have an ideal system for checking the validity of the Mott formula for the conductivity σ of liquid semiconductor, σ = σ Oe − E C−E F/kT We can also determine σ O by a combination of measurements of σ and the thermopower S. Results for S and are presented for a series of liquid alloys at and close to the stoichiometric composition MnTe and the results interpreted in terms of Eq. (1).