Dipole matrix elements and the nature of charge oscillation under coherent interband excitation in quantum wells

R. A. Coles, R. A. Abram, S. Brand, and M. G. Burt
Phys. Rev. B 60, 13306 – Published 15 November 1999
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Abstract

An empirical pseudopotential method is used to model two type-I quantum-well systems, allowing the investigation of interband dipole-matrix elements and charge oscillation under coherent optical excitation. Each relevant (microscopically varying) wave function is expressed as an exact envelope-function expansion to which various approximations are made, in analogy with envelope-function methods such as the kp model. The approximation to the quantum-well energy eigenfunctions of a single envelope function multiplying a band-edge zone-center state, the “atomic picture,” is shown to underestimate by orders of magnitude the interband dipole-matrix element. Including terms due to the second band edge, which play only a minor role in the exact envelope-function expansion, provides a good approximation to the true dipole-matrix element, which is significantly greater than the atomic picture predicts. In addition, the effect on the interband charge oscillation of omitting the second band-edge terms is shown to be a reduction of the oscillation from the width of the well to the atomic scale. These results confirm that the earlier results of Burt hold for realistic three-dimensional systems.

  • Received 2 October 1998

DOI:https://doi.org/10.1103/PhysRevB.60.13306

©1999 American Physical Society

Authors & Affiliations

R. A. Coles, R. A. Abram, and S. Brand

  • Department of Physics, University of Durham, Durham DH1 3LE, United Kingdom

M. G. Burt

  • BT Laboratories, Martlesham Heath, Ipswich, Suffolk IP5 3RE, United Kindgom

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Vol. 60, Iss. 19 — 15 November 1999

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