IBM Journal of Research and Development
IBM Skip to main content
  Home     Products & services     Support & downloads     My account  

  Select a country  
Journals Home  
  Systems Journal  
Journal of Research
and Development
    Current Issue  
    Recent Issues  
    Papers in Progress  
    Search/Index  
    Orders  
    Description  
    Patents  
    Recent publications  
    Author's Guide  
  Staff  
  Contact Us  
  Related links:  
     IBM Research  

IBM Journal of Research and Development  
Volume 32, Number 1, Page 82 (1988)
Basic Concepts in Quantum and Stochastic T...
  Full article: arrowPDF   arrowCopyright info





   

Band tails, path integrals, instantons, polarons, and all that

by M. H. Cohen, M.-Y. Chou, E. N. Economou, S. John, C. M. Soukoulis
This paper reviews the explanations recently developed by the authors and their collaborators of how disorder leads to exponential band tails and to Urbach tails in optical absorption. It starts with the simplest single-potential-well models which, despite their simplicity, are remarkably successful in accounting for the experimental facts. It then identifies the weaknesses, hidden or explicit, in these models and shows, step by step, how they can be corrected by increasing the sophistication of the procedures used. Exact results are finally achieved through use of field-theoretic techniques, and appropriately formulated single-potential-well models are shown to reproduce these quite accurately. It is also shown that the probability distribution of the random potential must be close to Gaussian, with an autocorrelation function which cuts off fairly rapidly with distance for there to be a well-defined, broad energy range in which there are exponential band tails in the density of states and Urbach tails in the optical absorption.
Related Subjects: Physics; Quantum theory and effects