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Observation of Excitonic n-Strings In A Quasi-one-Deviensional Charge-Transfer Crystal

Published online by Cambridge University Press:  16 February 2011

N. Peyghambarian
Affiliation:
University of Arizona, Optical Sciences Center and Physics Department, Tucson, AZ 85721
K. Meissner
Affiliation:
University of Arizona, Optical Sciences Center and Physics Department, Tucson, AZ 85721
B. Fluegel
Affiliation:
University of Arizona, Optical Sciences Center and Physics Department, Tucson, AZ 85721
S. Mazumdar
Affiliation:
University of Arizona, Optical Sciences Center and Physics Department, Tucson, AZ 85721
F. Guo
Affiliation:
University of Arizona, Optical Sciences Center and Physics Department, Tucson, AZ 85721
M. Kuwata-Gonokami
Affiliation:
University of Tokyo, Department of Applied Physics, Tokyo 113, Japan
Y. Sato
Affiliation:
University of Tokyo, Department of Applied Physics, Tokyo 113, Japan
K. Ema
Affiliation:
University of Tokyo, Department of Applied Physics, Tokyo 113, Japan
R. Shimano
Affiliation:
University of Tokyo, Department of Applied Physics, Tokyo 113, Japan
T. Tokihiro
Affiliation:
University of Tokyo, Department of Applied Physics, Tokyo 113, Japan
H. Ezaki
Affiliation:
University of Tokyo, Department of Applied Physics, Tokyo 113, Japan
E. Hanamura
Affiliation:
University of Tokyo, Department of Applied Physics, Tokyo 113, Japan
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Abstract

Collective excitations, such as plasmons, rotons, electron-hole liquid, and excitonic Molecules, have been extensively studied in condensed Matter.1 Wannier excitons in inorganic semiconductors are bound by the exchange interactions between two electrons of the exciton, and the bound state of More than two excitons is not possible. We demonstrate here a new type of collective excitations,2 bound states of Multiple charge-transfer (CT) excitons. Coulomb interactions in one dimension are shown to bind a train of several (More than two) CT excitons. Experimental evidence for these new type of elementary excitations is reported in a quasi-one-dimensional CT crystal of anthracene PMDA. High density excitation by femtosecond light pulses generates Multi-exciton chains, which we refer to as excitonic n-strings with n = 1, 2, 3, etc., along the stack axis of the crystal. Both the n = 2 excitonic string (biexciton) and the n = 3 string (tri-exciton) are observed. This report provides evidence for an n > 2 exciton chain in this system.2 The stability of the n-string exciton is supported by our theoretical calculations based on the extended Hubbard Hamiltonian in one dimension.

Type
Research Article
Copyright
Copyright © Materials Research Society 1994

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References

REFERENCES

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