Bond-operator representation of quantum spins: Mean-field theory of frustrated quantum Heisenberg antiferromagnets

We introduce a new representation of S=1/2 quantum spins in terms of bond operators. The bond operators create and annihilate singlet and triplet bonds between a pair of spins. The representation is useful in describing the transition between dimerized and magnetically ordered phases of quantum antiferromagnets. It is used to obtain a mean-field theory of the two-dimensional frustrated quantum Heisenberg antiferromagnets considered recently by Gelfand, Singh, and Huse. The method should also be useful in the analysis of random quantum antiferromagnets.

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