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5.4. VMC CALCULATIONS 129
(a)
(b)
(c)
(d)
Figure 5.10: Local expectation values (a,b,c) of the kinetic and exchange energies
of the projected BO/J wave-functions on each of the bonds within the unit-cell.
Width of filled square symbols is proportional to the (a) real and (b) imaginary
part of 〈c + i c j〉, and (c) to the local exchange energy 〈S i · S j 〉. The sign of the
imaginary part of the hopping bonds is according to the staggered flux pattern
(arrows). The wave-function has small charge density variations (d), therefore
we subtract the mean value n to the local density: size of circles are proportional
to 〈n i − n〉, and circles are open (filled) for negative (positive) sign. The biggest
circle corresponds to an on-site charge deviation of 2%. All the above results are
for l 0 =4andV 0 =5.