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Fix 2d heisenberg example and add error for bad unit cell inputs #88

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Merged
merged 4 commits into from
Oct 14, 2024
Merged

Fix 2d heisenberg example and add error for bad unit cell inputs #88

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bdb140a
Fix 2d heisenberg and add warning
ryanlevy Oct 11, 2024
f75c6e8
Cleanup
ryanlevy Oct 11, 2024
1a08e32
Add yperiodic option
ryanlevy Oct 14, 2024
bbb6106
Negative sign fix
ryanlevy Oct 14, 2024
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10 changes: 8 additions & 2 deletions examples/vumps/vumps_2d_heisenberg.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@ conserve_qns = true
solver_tol = (x -> x / 10)
outer_iters = 10 # Number of times to increase the bond dimension
width = 4
yperiodic = false # OBC vs cylinder

##############################################################################
# CODE BELOW HERE DOES NOT NEED TO BE MODIFIED
Expand All @@ -30,7 +31,7 @@ initstate(n) = isodd(n) ? "↑" : "↓"
s = infsiteinds("S=1/2", N; conserve_qns, initstate)
ψ = InfMPS(s, initstate)

function ITensorInfiniteMPS.unit_cell_terms(::Model"heisenberg2D"; width)
function ITensorInfiniteMPS.unit_cell_terms(::Model"heisenberg2D"; width, yperiodic)
opsum = OpSum()
for i in 1:width
# Vertical
Expand All @@ -42,12 +43,17 @@ function ITensorInfiniteMPS.unit_cell_terms(::Model"heisenberg2D"; width)
opsum += -0.5, "S-", i, "S+", i + width
opsum += "Sz", i, "Sz", i + width
end
if yperiodic
opsum += -0.5, "S+", 1, "S-", width
opsum += -0.5, "S-", 1, "S+", width
opsum += "Sz", 1, "Sz", width
end
return opsum
end
model = Model("heisenberg2D")

# Form the Hamiltonian
H = InfiniteSum{MPO}(model, s; width)
H = InfiniteSum{MPO}(model, s; width, yperiodic)

# Check translational invariance
# println("\nCheck translation invariance of the initial VUMPS state")
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