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100 CHAPTER 4. HONEYCOMB LATTICE
-0.542
3/2
-0.544
-0.546
2D
CNT (2,2)
CNT (3,0)
CNT (4,0)
CNT (2,1)
CNT (3,1)
CNT (3,2)
-0.548
0 0.01 0.02
1/N
Figure 4.10: Scaling of the Heisenberg energy per site (t − J model at half-filling)
for our best variational wavefunction.
In order to compare further with the QMC, we have calculated the energy
per site and staggered magnetization per site for different nanotube lengths, such
that we could extrapolate the result in the thermodynamic limit (see Fig. 4.10,
4.11, and Table 4.3). Unexpectedly, we find that the AF/RV B wavefunction is
still a good Ansatz for the nanotubes at half-filling.