The smooth structural change in mesoscopic Peierls chains |
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Authors: | I Bâldea H Köppel LS Cederbaum |
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Institution: | Theoretische Chemie, Physikalisch-Chemisches Institut, Universit?t Heidelberg, Im Neuenheimer Feld 253, 69120, Heidelberg, Germany
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Abstract: | We investigate the Peierls transition in finite chains by exact (Lanczos) diagonalization and within a seminumerical method
based on the factorization of the electron-phonon wave function (Adiabatic Ansatz, AA). AA can be applied for mesoscopic chains
up to micrometer sizes and its reliability can be checked self-consistently. Our study demonstrates the important role played
for finite systems by the tunneling in the double well potential. The chains are dimerized only if their size N exceeds a critical value Nc which increases with increasing phonon frequency. Quantum phonon fluctuations yield a broad transition region. This smooth Peierls transition contrasts not only to the sharp mean field transition, but also with the sharp RPA soft mode instability,
although RPA partially accounts for quantum phonon fluctuations. For weak coupling the dimerization disappears below micrometer
sizes; therefore, this effect could be detected experimentally in mesoscopic systems.
Received: 3 January 1998 / Revised: 13 March 1998 / Accepted: 3 April 1998 |
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Keywords: | PACS 63 22 +m Phonons in low-dimensional structures and small particles - 63 20 -e Phonons in crystal lattices - 71 45 Lr Charge-density-wave systems |
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