Physics – Condensed Matter – Strongly Correlated Electrons
Scientific paper
1999-03-09
Phys. Rev. B 60, 14613 (1999)
Physics
Condensed Matter
Strongly Correlated Electrons
4 pages, 4 figures, small changes, published version
Scientific paper
10.1103/PhysRevB.60.14613
We analyze the stability of the spontaneously dimerized spin-liquid phase of the frustrated Heisenberg antiferromagnet - the J1-J2 model. The lowest triplet excitation, corresponding to breaking of a singlet bond, is found to be stable in the region 0.38 < J2/J1 < 0.62. In addition we find a stable low-energy collective singlet mode, which is closely related to the spontaneous violation of the discrete symmetry. Both modes are gapped in the quantum disordered phase and become gapless at the transition point to the Neel ordered phase (J2/J1=0.38). The spontaneous dimerization vanishes at the transition and we argue that the disappearance of dimer order is related to the vanishing of the singlet gap. We also present exact diagonalization data on a small (4x4) cluster which indeed show a structure of the spectrum, consistent with that of a system with a four-fold degenerate (spontaneously dimerized) ground state.
Kotov Valeri N.
Oitmaa Jaan
Sushkov Oleg P.
Weihong Zheng
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