Dresden 2003 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 7: Niedrigdimensionale Systeme
TT 7.7: Vortrag
Dienstag, 25. März 2003, 11:15–11:30, HSZ03
Field-doping of C60 crystals: A view from theory — •Erik Koch1, Samuel Wehrli2, Manfred Sigrist2, and Olle Gunnarsson1 — 1Max-Planck-Institut für Festkörperforschung, 70569 Stuttgart — 2Theoretische Physik, ETH-Hönggerberg, CH-8093 Zürich
The proposal of using the field-effect for doping organic crystals has
raised enormous interest.
To assess the feasibility of such an approach, we investigate the effect
of a strong electric field on the electronic structure of C60
crystals. Calculating the polarization of the molecules and splittings
of the molecular levels as a function of the external field, we determine
up to what field-strengths the electronic structure of C60 is still
essentially unchanged, so that one can speak of field-effect doping,
in the sense of putting charge carriers into otherwise unchanged states.
Beyond these field strengths, the electronic structure changes so much,
that one can no longer speak of a doped system.
In addition we address the question of a metal-insulator transition
at integer dopings and briefly review proposed mechanisms for explaining an
increase
of the superconducting transition temperature in field-doped C60
that is intercalated with haloform molecules.