[tetku.py] Add square d-wave and s-wave BCS model.

tetraku/tetraku/models/bcs/__init__.py

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+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+# Copyright (C) 2022-2023 Hao Zhang<[email protected]>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+#

tetraku/tetraku/models/bcs/square/__init__.py

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+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+# Copyright (C) 2022-2023 Hao Zhang<[email protected]>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+#

tetraku/tetraku/models/bcs/square/d_wave.py

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+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+# Copyright (C) 2021-2023 Hao Zhang<[email protected]>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+#
+
+import TAT
+import tetragono as tet
+
+
+def abstract_state(L1, L2, t, Delta, mu):
+    """
+    Create BCS d-wave model state.
+
+    Parameters
+    ----------
+    L1, L2 : int
+        The lattice size.
+    t, Delta : float
+        BCS model parameters.
+    mu : float
+        chemical potential.
+    """
+    state = tet.AbstractState(TAT.Parity.D.Tensor, L1, L2)
+    state.physics_edges[...] = [(False, 2), (True, 2)]
+
+    CSCS = tet.common_tensor.Parity_Hubbard.CSCS.to(float)
+
+    N0 = tet.common_tensor.Parity_Hubbard.N0.to(float)
+    N1 = tet.common_tensor.Parity_Hubbard.N1.to(float)
+    N = N0 + N1
+
+    state.hamiltonians["vertical_bond"] = -t * CSCS + Delta * tet.common_tensor.Parity_Hubbard.singlet.to(float)
+    state.hamiltonians["horizontal_bond"] = -t * CSCS - Delta * tet.common_tensor.Parity_Hubbard.singlet.to(float)
+    state.hamiltonians["single_site"] = -mu * N
+    return state
+
+
+def abstract_lattice(L1, L2, D, t, Delta, mu):
+    """
+    Create BCS model lattice.
+
+    Parameters
+    ----------
+    L1, L2 : int
+        The lattice size.
+    D : int
+        The cut dimension.
+    t, Delta : float
+        BCS model parameters.
+    mu : float
+        chemical potential.
+    """
+    state = tet.AbstractLattice(abstract_state(L1, L2, t, Delta, mu))
+    D0 = D // 2
+    D1 = D - D0
+    state.virtual_bond["R"] = state.virtual_bond["D"] = [(False, D0), (True, D1)]
+
+    return state

tetraku/tetraku/models/bcs/square/s_wave.py

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+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+# Copyright (C) 2021-2023 Hao Zhang<[email protected]>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+#
+
+import TAT
+import tetragono as tet
+
+
+def abstract_state(L1, L2, t, Delta, mu):
+    """
+    Create BCS d-wave model state.
+
+    Parameters
+    ----------
+    L1, L2 : int
+        The lattice size.
+    t, Delta : float
+        BCS model parameters.
+    mu : float
+        chemical potential.
+    """
+    state = tet.AbstractState(TAT.Parity.D.Tensor, L1, L2)
+    state.physics_edges[...] = [(False, 2), (True, 2)]
+
+    CSCS = tet.common_tensor.Parity_Hubbard.CSCS.to(float)
+
+    N0 = tet.common_tensor.Parity_Hubbard.N0.to(float)
+    N1 = tet.common_tensor.Parity_Hubbard.N1.to(float)
+    N = N0 + N1
+
+    state.hamiltonians["vertical_bond"] = -t * CSCS + Delta * tet.common_tensor.Parity_Hubbard.singlet.to(float)
+    state.hamiltonians["horizontal_bond"] = -t * CSCS + Delta * tet.common_tensor.Parity_Hubbard.singlet.to(float)
+    state.hamiltonians["single_site"] = -mu * N
+    return state
+
+
+def abstract_lattice(L1, L2, D, t, Delta, mu):
+    """
+    Create BCS model lattice.
+
+    Parameters
+    ----------
+    L1, L2 : int
+        The lattice size.
+    D : int
+        The cut dimension.
+    t, Delta : float
+        BCS model parameters.
+    mu : float
+        chemical potential.
+    """
+    state = tet.AbstractLattice(abstract_state(L1, L2, t, Delta, mu))
+    D0 = D // 2
+    D1 = D - D0
+    state.virtual_bond["R"] = state.virtual_bond["D"] = [(False, D0), (True, D1)]
+
+    return state