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Dimer versus twist order in the J 1 - J 2 model

1990; American Physical Society; Volume: 65; Issue: 8 Linguagem: Inglês

10.1103/physrevlett.65.1072

1092-0145

Rajiv R. P. Singh, Rajamani Narayanan,

Theoretical and Computational Physics

We diagonalize fully the 4\ifmmode\times\else\texttimes\fi{}4 S=1/2 Heisenberg model with nearest-neighbor (${\mathit{J}}_{1}$) and second-neighbor (${\mathit{J}}_{2}$) exchanges for several values of ${\mathit{J}}_{2}$/${\mathit{J}}_{1}$. For ${\mathit{J}}_{2}$/${\mathit{J}}_{1}$\ensuremath{\approxeq}1/2 the specific heat shows a peak near T=0.27${\mathit{J}}_{1}$, and the dimer order increases sharply around that temperature. In contrast, the twist order considered earlier by Dagotto and Moreo drops below that temperature, and its T=0 value is roughly the same as that at T=\ensuremath{\infty}. This shows that while the system may develop long-range dimer order (and it certainly has appreciable short-range dimer order) for these values of ${\mathit{J}}_{2}$/${\mathit{J}}_{1}$, there is no indication of enhanced twist order.