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# Small Polarons in Dense Lattice Systems

Ramakrishnan, TV and Pai, Venketeswara G (2002) Small Polarons in Dense Lattice Systems. In: Journal of Low Temperature Physics, 126 (3-4). pp. 1055-1065.

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## Abstract

There is considerable evidence for the persistence of small polaron-like entities in colossal magnetoresistance oxides, which are dense electronic systems with electron density $n^{<}_{\approx}1$ per site. This has brought up again the question of whether and how small (narrow band) polaronic states survive in a dense electronic system. We investigate this question, in a simple one band Holstein polaron model, in which spinless electrons on a tight binding lattice cause an on-site lattice distortion $x_0$. In the small polaron limit, each electron is localized, and the electron hopping $t_i_j$ is neglected. We develop a systematic approach in powers of $t_i_j$, identify classical $t^0$, quantum mean field $t^1$, and quantum fluctuation $t^2$ terms, and show that the last two terms are relatively small, even for dense systems, so long as the narrowed polaron bandwidth t*=t exp(-u) is much smaller than the Einstein phonon energy $\hbar \omega _0$. (Here u=$(x^2{} _0 /2x ^2_{}z_p)$ with $x_z_p$ being the zero point phonon displacement.) The relevance of these results for CMR oxides is briefly discussed.

Item Type: Journal Article Copyright of this article belongs to Springer. Division of Physical & Mathematical Sciences > Physics 02 Jun 2006 27 Aug 2008 12:10 http://eprints.iisc.ernet.in/id/eprint/7499

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