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Metal insulator transition

Contact : vinh.ta-phuoc@univ-tours.fr / mustapha.zaghrioui@univ-tours.fr

Our group is mainly interested in using optical and Raman spectroscopy to investigated vibrational properties and electrodynamics of strongly correlated, multiferroic materials.

Strongly correlated systems – Metal-insulator transition

Mott insulators represent a large class of materials with half-filled d or f orbitals that should be metallic according to conventional band theory, but are actually insulators. In these systems, the on-site electron-electron repulsion U, not included in the conventional band theory, leads to an insulating ground state when U is significantly larger than the half-bandwidth D. An interesting characteristic of Mott insulators is that external perturbations may provoke insulator to metal transitions (IMT).

For example, it occurs by the application of chemical or physical pressure which enhances the bandwidth. Similarly a deviation from half-filling caused by an electronic doping also induces an IMT. During the last quarter century, outstanding electronicproperties were discovered in the vicinity of such metal-insulator transitions : superconductivity in copper oxides, molecular systems κ-(BEDT-TTF)2 X and iron chalcogenides, colossal magnetoresistance in manganites or thermoelectricity with large figure of merit in different doped Mott insulators including cobaltites, ... 
 





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