Showing papers on "Mott transition published in 1970"

Screening and Stark Effects Due to Impurities on Excitons in Semiconductors

Abstract: It is pointed out that localized donor electrons participate dominantly in screening the electron-hole Coulomb attraction in the exciton around the donor concentration where the Mott transition is ...

Metal-insulator transition in transition metal oxides

Abstract: The metal-insulator transition in the V2O3 system is discussed. A recent series of experiments on V2O3 and (V1-xCrx)2O3 is reviewed. The phase diagram fort he system is described. The Cr-doped mixed oxides are insulating at room temperature for x ≥ 0.009 and transform to a metal with the application of pressure. This phase transition is identified as a Mott transition. A comparison is made between the experimental results and theoretical predictions of the Mott transition.

Bistable switching and the Mott transition

Abstract: Attention is given to some aspects of the early development of solid state switching, followed by an hypothesis as to the relation of the Mott transition to the bistable switching cycle. The action in stibnite (Sb2S3) is cited, and data are appended which a good theory must account for.

Metal-insulator transition; nucleation of a conducting phase in amorphous semiconductors

Abstract: The amorphous semiconductors are assumed to be capable of existing in two distinct thermodynamic states, an insulating state at low temperature and a “metallic” state at high temperature. The thermodynamics of Mott transition is considered in a framework of field dependent equilibrium free carrier concentration at the lattice temperature, and neither avalanche multiplication or hot electron are assumed. The switching effect observed in amorphous semiconductors is analysed as a phenomenon of nucleation and growth of a conducting ‘metallic’ phase. We are considering purely electronic phases, and no irreversible structural rearrangement is assumed involved. The threshold electric field at which insulator-metallic transition is achieved is shown to be a relevant nucleation field. This is thus a phase transition of an electron fluid from low density electron with perfect gas behaviour (insulating state) to a high density liquid behaviour (metallic state).

Positron Annihilation in Concentrated Cesium–Ammonia Solutions

Abstract: The momentum distribution of photons from positrons annihilating in liquid and solid cesium–ammonia solutions was found to be concentration dependent. The narrow component was found to broaden with increasing concentration. The results are compared with those obtained for pure cesium, and one is led to believe that a bound species is formed in these solutions even at very high concentrations. No evidence of a Mott transition is found in cesium–ammonia solutions, and no abrupt change is found in the shape of the momentum distribution in going from 22 to 94 mole % cesium in ammonia. A conduction‐electron‐type analysis is presented for the density of states and the probability density. Methods of preparing relatively stable cesium–ammonia solutions are discussed in some detail.

Magnetic field dependence of the metal-insulator 'Mott transition': a study of the compound VO2

Abstract: A theory of the metal-insulator transition, taking into account the effects of an external magnetic field is presented. Comparison with experimental susceptibility and optical data for VO2 is good and yields for theoretical parameters the values: Intra-atomic Coulomb integral I approximately=0.7 eV; density of states N(Ef) approximately=1023 cm-3 eV-1 ratio IN(Ef)/N approximately=10; optical energy gap Eg approximately=0.7 eV. The insulating phase stability criterion is shown to be identical with Mott's. The existence of a critical field Hc such that higher magnetic fields destroy the insulating phase is derived.