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Renormalización de la brecha de banda π-π* inducida por la foto en el grafito
S Pagliara1, G Galimberti, S Mor
1Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, I-25121 Brescia, Italy.
Journal of the American Chemical Society
|April 2, 2011
Resumen
Los pulsos láser UV reducen transitoriamente la brecha de banda π-π* en el grafito en 500 meV. Este efecto fotoinducido, observado en condiciones de no equilibrio, afecta las propiedades electrónicas de los materiales de carbono.
Área de la Ciencia:
- Física de la materia condensada Física de la materia condensada
- Ciencia de los materiales Ciencia de los materiales.
- La Química Física es la química física.
Sus antecedentes:
- Las propiedades electrónicas de los alótropos de carbono están dictadas por sus orbitales π.
- Comprender el comportamiento fotoinducido y no equilibrado de estos orbitales es crucial.
- Se está investigando el comportamiento transitorio de los orbitales π en grafito bajo excitación láser.
Objetivo del estudio:
- Para investigar el comportamiento de no equilibrio fotoinducido de los orbitales π en grafito.
- Para demostrar la renormalización de la brecha de banda π-π* en el grafito bajo excitación láser UV.
- Para cuantificar el cambio transitorio en la brecha de banda π-π*.
Principales métodos:
- Excitación del grafito con un pulso láser UV para lograr altas densidades de portadores.
- Detección de la reflectividad transitoria y el tiempo de desintegración utilizando una sonda infrarroja.
- Ajuste de la energía fotónica de la bomba UV a través de la resonancia de absorción π-π*.
Principales resultados:
- Se observó una renormalización transitoria de la brecha de banda π-π* cuando la densidad de la portadora excedió el 10% de la densidad π* de los estados.
- La reflectividad transitoria máxima y el tiempo de desintegración se produjeron a una energía de fotones desplazada hacia abajo en 500 meV desde el máximo de absorción de equilibrio.
- Este desplazamiento hacia abajo indica una brecha de banda π-π* transitoria que se reduce cerca del punto M de la zona de Brillouin.
Conclusiones:
- La fotoexcitación puede inducir una contracción significativa y transitoria de la brecha de banda π-π* en el grafito.
- La renormalización de la brecha de banda observada es un fenómeno de no equilibrio impulsado por altas densidades de portadores.
- Este hallazgo ofrece información sobre el comportamiento electrónico dinámico de los materiales de carbono bajo luz intensa.
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