@@ -1301,7 +1301,10 @@ <h3 id="subproblems">Subproblems</h3>
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{\mathbf{a}_1} = (0,a),
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\]</ div >
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< div class ="arithmatex "> \[
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- {\mathbf{a}_2} = (\sqrt 3 a/2, - a/2),{\mathbf{a}_3} = ( - \sqrt 3 a/2, - a/2)
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+ {\mathbf{a}_2} = (\sqrt 3 a/2, - a/2),
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+ \]</ div >
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+ < div class ="arithmatex "> \[
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+ {\mathbf{a}_3} = ( - \sqrt 3 a/2, - a/2)
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\]</ div >
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< div class ="arithmatex "> \[
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{\mathbf{b}_1} = {\mathbf{a}_2} - {\mathbf{a}_3} = (\sqrt 3 a,0),
@@ -1312,14 +1315,21 @@ <h3 id="subproblems">Subproblems</h3>
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< div class ="arithmatex "> \[
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{\mathbf{b}_3} = {\mathbf{a}_1} - {\mathbf{a}_2} = ( - \sqrt 3 a/2,3a/2)
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\]</ div >
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- < p > Then the Haldane model on a hexagonal lattice can be written as
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- < span class ="arithmatex "> \(< span class ="arithmatex "> \(H(k) = {d_0}I + {d_1}{\sigma _1} + {d_2}{\sigma _2} + {d_3}{\sigma _3}\)</ span > \)</ span >
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- < span class ="arithmatex "> \(< span class ="arithmatex "> \({d_0} = 2{t_2}\cos \phi \sum\nolimits_i {\cos (\mathbf{k} \cdot {\mathbf{b}_i})} = 2{t_2}\cos \phi \left[ {\cos \left( {\sqrt 3 {k_x}a} \right) + \cos \left( { - \sqrt 3 {k_x}a/2 + 3{k_y}a/2} \right) + \cos \left( { - \sqrt 3 {k_x}a/2 - 3{k_y}a/2} \right)} \right]\)</ span > \)</ span >
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- $$
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- {d_1} = {t_1}\sum\nolimits_i {\cos (\mathbf{k} \cdot {\mathbf{a}_i})} = {t_1}\left[ {\cos \left( {{k_y}a} \right) + \cos \left( {\sqrt 3 {k_x}a/2 - {k_y}a/2} \right) + \cos \left( { - \sqrt 3 {k_x}a/2 - {k_y}a/2} \right)} \right]\
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- {d_2} = {t_1}\sum\nolimits_i {\sin (\mathbf{k} \cdot {\mathbf{a}_i})} = {t_1}\left[ {\sin \left( {{k_y}a} \right) + \sin \left( {\sqrt 3 {k_x}a/2 - {k_y}a/2} \right) + \sin \left( { - \sqrt 3 {k_x}a/2 - {k_y}a/2} \right)} \right] \
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- {d_3} = m - 2{t_2}\sin \phi \sum\nolimits_i {\sin (\mathbf{k} \cdot {\mathbf{b}_i})} = m - 2{t_2}\sin \phi \left[ {\sin \left( {\sqrt 3 {k_x}a} \right) + \sin \left( { - \sqrt 3 {k_x}a/2 + 3{k_y}a/2} \right) + \sin \left( { - \sqrt 3 {k_x}a/2 - 3{k_y}a/2} \right)} \right] \
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- $$</ p >
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+ < p > Then the Haldane model on a hexagonal lattice can be written as</ p >
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+ < div class ="arithmatex "> \[
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+ H(k) = {d_0}I + {d_1}{\sigma _1} + {d_2}{\sigma _2} + {d_3}{\sigma _3}
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+ \]</ div >
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+ < div class ="arithmatex "> \[{d_0} = 2{t_2}\cos \phi \sum\nolimits_i {\cos (\mathbf{k} \cdot {\mathbf{b}_i})} = 2{t_2}\cos \phi \left[ {\cos \left( {\sqrt 3 {k_x}a} \right) + \cos \left( { - \sqrt 3 {k_x}a/2 + 3{k_y}a/2} \right) + \cos \left( { - \sqrt 3 {k_x}a/2 - 3{k_y}a/2} \right)} \right]$$
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+ \]</ div >
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+ < div class ="arithmatex "> \[
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+ {d_1} = {t_1}\sum\nolimits_i {\cos (\mathbf{k} \cdot {\mathbf{a}_i})} = {t_1}\left[ {\cos \left( {{k_y}a} \right) + \cos \left( {\sqrt 3 {k_x}a/2 - {k_y}a/2} \right) + \cos \left( { - \sqrt 3 {k_x}a/2 - {k_y}a/2} \right)} \right]\\
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+ \]</ div >
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+ < div class ="arithmatex "> \[
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+ {d_2} = {t_1}\sum\nolimits_i {\sin (\mathbf{k} \cdot {\mathbf{a}_i})} = {t_1}\left[ {\sin \left( {{k_y}a} \right) + \sin \left( {\sqrt 3 {k_x}a/2 - {k_y}a/2} \right) + \sin \left( { - \sqrt 3 {k_x}a/2 - {k_y}a/2} \right)} \right] \\
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+ \]</ div >
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+ < div class ="arithmatex "> \[
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+ {d_3} = m - 2{t_2}\sin \phi \sum\nolimits_i {\sin (\mathbf{k} \cdot {\mathbf{b}_i})} = m - 2{t_2}\sin \phi \left[ {\sin \left( {\sqrt 3 {k_x}a} \right) + \sin \left( { - \sqrt 3 {k_x}a/2 + 3{k_y}a/2} \right) + \sin \left( { - \sqrt 3 {k_x}a/2 - 3{k_y}a/2} \right)} \right] \\
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+ \]</ div >
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< p > where < span class ="arithmatex "> \(\sigma_i\)</ span > are the Pauli matrices and < span class ="arithmatex "> \(I\)</ span > is the identity matrix.
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< div class ="highlight "> < pre > < span > </ span > < code > < span class ="k "> def</ span > < span class ="nf "> calc_hamiltonian</ span > < span class ="p "> (</ span > < span class ="n "> kx</ span > < span class ="p "> ,</ span > < span class ="n "> ky</ span > < span class ="p "> ,</ span > < span class ="n "> a</ span > < span class ="p "> ,</ span > < span class ="n "> t1</ span > < span class ="p "> ,</ span > < span class ="n "> t2</ span > < span class ="p "> ,</ span > < span class ="n "> phi</ span > < span class ="p "> ,</ span > < span class ="n "> m</ span > < span class ="p "> ):</ span >
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< span class ="w "> </ span > < span class ="sd "> """</ span >
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