説明
<jats:title>Abstract</jats:title><jats:p>Elliott's work on exciton effects at the direct absorption edge is extended to include other van Hove singularities and deviations from the effective mass approximation. The sum rule which replaces the <jats:italic>f</jats:italic>‐sum rule in this case is derived. The Koster‐Slater and Coulomb interactions are treated as limiting cases. Due to the electron‐hole interaction, the <jats:italic>M</jats:italic><jats:sub>0</jats:sub> and <jats:italic>M</jats:italic><jats:sub>1</jats:sub> branch‐points of ϵ<jats:sub>2</jats:sub> are enhanced and sharpened, whilst the <jats:italic>M</jats:italic><jats:sub>2</jats:sub> and <jats:italic>M</jats:italic><jats:sub>3</jats:sub> branch‐points are weakened and smoothed out. Only the <jats:italic>M</jats:italic><jats:sub>0</jats:sub> points generate (quasi) discrete levels; no evidence for these is found near the <jats:italic>M</jats:italic><jats:sub>1</jats:sub> points. For a very prolate <jats:italic>M</jats:italic><jats:sub>1</jats:sub> singularity, certain branch‐points appear asymptotically below the critical energy.</jats:p>
収録刊行物
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- physica status solidi (b)
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physica status solidi (b) 16 (1), 147-157, 1966-01
Wiley