[Instabilité de Herzfeld versus transition de Mott dans les solutions de métaux dans l'ammoniac]
Bien que la plupart des transitions isolant–métal dans les semiconducteurs dopés soient interprétées comme des transitions de Mott, certains systèmes semblent échapper à ce scénario. Les solutions de métaux alcalins dans l'ammoniac en sont un brillant exemple. Elles présentent une séparation de phase dans la gamme de concentration pour laquelle la transition isolant–métal se produit. En utilisant des approximations adéquates pour les fluides quantiques polarisables, nous montrons que l'origine de la transition isolant–métal dans ce système est probablement similaire à celle proposée il y a longtemps par Herzfeld, c'est-à-dire, due aux fluctuations des électrons solvatés. Nous montrons également pourquoi la séparation de phase peut apparaître : l'instabilité de Herzfeld de l'isolant se produit à une concentration pour laquelle la phase métallique est aussi instable. En conséquence, la transition de Mott ne peut pas se produire à basse température. Le scénario proposé ouvre de nouvelles perspectives pour la transition isolant–métal en physique de la matière condensée.
Although most metal–insulator transitions in doped insulators are generally viewed as Mott transitions, some systems seem to deviate from this scenario. Alkali metal–ammonia solutions are a brilliant example of this. They reveal a phase separation in the range of metal concentrations where a metal–insulator transition occurs. Using a mean spherical approximation for quantum polarizable fluids, we argue that the origin of the metal–insulator transition in such a system is likely to be similar to that proposed by Herzfeld a long time ago, namely, due to fluctuations of solvated electrons. We also show how the phase separation may appear: the Herzfeld instability of the insulator occurs at a concentration for which the metallic phase is also unstable. As a consequence, the Mott transition cannot occur at low temperature. The proposed scenario may provide a new insight into the metal–insulator transition in condensed-matter physics.
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Mots-clés : Electrons solvatés, Transition de Mott, Séparation de phase
Gennady N. Chuev 1, 2 ; Pascal Quémerais 3
@article{CRPHYS_2007__8_3-4_449_0,
author = {Gennady N. Chuev and Pascal Qu\'emerais},
title = {Herzfeld instability versus {Mott} transition in metal{\textendash}ammonia solutions},
journal = {Comptes Rendus. Physique},
pages = {449--455},
publisher = {Elsevier},
volume = {8},
number = {3-4},
year = {2007},
doi = {10.1016/j.crhy.2007.05.016},
language = {en},
}
Gennady N. Chuev; Pascal Quémerais. Herzfeld instability versus Mott transition in metal–ammonia solutions. Comptes Rendus. Physique, Optical techniques for direct imaging of exoplanets, Volume 8 (2007) no. 3-4, pp. 449-455. doi : 10.1016/j.crhy.2007.05.016. https://comptes-rendus.academie-sciences.fr/physique/articles/10.1016/j.crhy.2007.05.016/
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