Charge states of strongly correlated 3d oxides: from typical insulator to unconventional electron-hole Bose liquid

• Опубліковано в: : Физика низких температур
• Дата: 2007
• Автор: Moskvin, A.S.
• Формат: Стаття
• Мова: Англійська
• Опубліковано: Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України 2007
• Теми: Новые электронные материалы и системы
• Онлайн доступ: https://nasplib.isofts.kiev.ua/handle/123456789/127739
• Назва журналу: Digital Library of Periodicals of National Academy of Sciences of Ukraine
• Цитувати: Charge states of strongly correlated 3d oxides: from typical
 insulator to unconventional electron-hole Bose liquid / A.S. Moskvin // Физика низких температур. — 2007. — Т. 33, № 2-3. — С. 314-327. — Бібліогр.: 34 назв. — англ.

We present a model approach to describe charge fluctuations and different charge phases in
 strongly correlated 3d oxides. As a generic model system one considers that of centers each with
 three possible valence states M⁰, described in frames of S 1 pseudospin (isospin) formalism by
 an effective anisotropic non-Heisenberg Hamiltonian which includes both two types of single particle
 correlated hopping and the two-particle hopping. Simple uniform mean-field phases include
 an insulating monovalent M⁰ phase, mixed-valence binary (disproportionated) M phase, and
 mixed-valence ternary («under-disproportionated») M⁰, phase. We consider two first phases in
 more details focusing on the problem of electron-hole states and different types of excitons in
 M⁰ phase and formation of electron-hole Bose liquid in M phase. Pseudospin formalism provides
 a useful framework for revealing and describing different topological charge fluctuations, in particular,
 like domain walls or bubble domains in antiferromagnets. Electron-lattice polarization effects
 are shown to be crucial for the stabilization of either phase. All the insulating systems such as
 M0 phase are subdivided to two classes: stable and unstable ones with regard to the formation of
 self-trapped charge transfer (CT) excitons. The latter systems appear to be unstable with regard to
 the formation of CT exciton clusters, or droplets of the electron-hole Bose liquid. The model approach
 suggested is believed to be applied to describe a physics of strongly correlated oxides such
 as cuprates, manganites, bismuthates, and other systems with charge transfer excitonic instability
 and/or mixed valence. We shortly discuss an unconventional scenario of the essential physics of
 cuprates which implies their instability with regard to the self-trapping of charge transfer excitons
 and the formation of electron-hole Bose liquid.