Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

The metal-insulator transition in mesoscopic and macroscopic systems

3 The metal-insulator transition in mesoscopic and macroscopic systems [Pg.1463]

In a series of seminal contributions beginning in 1949, Sir Nevill Mott first posed the key question of how such an insulating, non-metallic system could naturally evolve into a metallic system. His conclusion, that such a system could undergo an insulator-to-metal transition, was perhaps not surprising what was remarkable, however, was Mott s proposal that at the very transition from insulator to metal, all the outer (valence) electrons would become free at once, not just a few [Pg.1463]

The ramifications for a Gedanken experiment at T = 0 K are sketched in Fig. 4a, revealing the d.c. electrical conductivity for a macroscopic system such as Si P in which d, the average distance between one-electron centers, can be continuously tuned by changes in the composition of the system. For values of d below a critical distance, dc, i.e. d 4) the system is metallic and the electronic wave-function is completely delocalized over the entire sample. For very large d d dfj, we have an insulator with a valence electron wavefunction that is completely localized at the individual atomic sites. At a critical distance, d we then have, according to Mott, a first-order (discontinuous) metal-insulator transition. Thus, at r = 0 K one either has a non-metal or an insulator, for which the limiting (low temperature) d.c. electrical conductivity is zero, or a metal, with a finite conductivity at this base temperature. Whether the metal-insulator transition in Si P (Fig. 4a) is continuous or discontinuous is still a source of controversy. [Pg.1464]

There is therefore a clear distinction to be made here between the nature of the metal insulator transition in a macroscopic system such as Si P and our (assumed) inevitable metal-insulator transition occurring solely within an isolated microscopic cluster or particle, typically containing between 10 and 10 atoms (Fig. 1). [Pg.1464]

In his celebrated papeF of 1961, The Transition to the Metallic State , Mott also alluded to the fundamental differences between these two situations. Concerning the proposed first-order (discontinuous) nature of the metal-insulator transition in macroscopic systems, he noted ... the sharp transition described here is only expected in an infinite lattice. It goes without saying that for a finite number of atoms there will be a gradual decrease in the weight of the ionized states in the wave function as the interatomic distance is increased, or, in other words, a gradual transition  [Pg.1464]




SEARCH



Insulated system

Macroscopic metals

Mesoscopic

Mesoscopic system

Mesoscopics

Metal-insulator transition

Metals and Insulators

The metal-insulator transition

Transit system

Transition metal systems

© 2024 chempedia.info