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SUMMARY:The Transient Localization Scenario for Charge Transport in Crysta
 lline Organic Materials - Professor Simone Fratini\, CNRS
DTSTART:20160125T143000Z
DTEND:20160125T153000Z
UID:TALK63270@talks.cam.ac.uk
CONTACT:Stuart Higgins
DESCRIPTION:The mobility in crystalline organic semiconductors is believed
  to be intrinsically limited by the presence of large thermal molecular mo
 tions\, which are a direct consequence of the weak Van der Waals inter-mol
 ecular bonds. These lead to a breakdown of the usual assumptions of semicl
 assical transport\, suggesting that strongly localized carriers are a more
  natural starting point than free carriers to describe the dynamics of cha
 rge carriers in these materials. In this scenario\, termed "transient loca
 lization"\, quantum localization of the carriers occurs on short time scal
 es and is eventually destroyed by the dynamical nature of molecular fluctu
 ations\, leading to unconventional charge transport.\n\nI will explore suc
 h transient localization mechanism reviewing both microscopic model calcul
 ations and a recently developed phenomenological approach which provides u
 seful analytical formulas for the analysis of experiments. I will show tha
 t the theory can consistently explain several characteristic experimental 
 features of organic semiconductors\, such as the low values of the mobilit
 y\, its power-law temperature dependence\, the crossover to a thermally ac
 tivated behavior in the presence of extrinsic disorder\, as well as the ob
 served non-Drude like behavior of the optical conductivity. Finally I will
  mention some analogies with other families of organic materials such as o
 rganic conductors and superconductors suggesting that transient localizati
 on could be a universal characteristic of organic matter.
LOCATION:Kapitza Building Seminar Room\, Cavendish Laboratory\, Department
  of Physics
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