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Commit 57feedd4 authored by Matthew Bunney's avatar Matthew Bunney
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Editing irrep section

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......@@ -44,7 +44,7 @@ superscriptaddress, floatfix, longbibliography]{revtex4-2}
\node[shape=circle,draw,inner sep=1pt] (char) {#1};}}
\MakeRobustCommand\circled
\newcommand{\su}{SU}
\newcommand{\su}[1]{SU(#1)}
\newcommand{\bvec}[1]{\boldsymbol #1}
\newcommand{\Ucrit}{U_\mathrm{c}}
......@@ -301,9 +301,9 @@ presented in the following.
\begin{tabular}{cccc} \toprule
{$\gamma$} & Spatial & Spin & Total \\ \hline
\sym A 1 & \numberedHexagon{$\Delta_s$}{1}{1}{1}{1}{1}{1}
& $d_0$
& $\Psi$
& $\begin{gathered}
\Delta_{s} d_0 \\
\Delta_{s} \Psi \\
\Delta_{p_x} d_x - \Delta_{p_y} d_y
\end{gathered}$ \\
\sym A 2 & --- & $d_z$
......@@ -339,7 +339,7 @@ presented in the following.
\begin{bmatrix}
\Delta_{d_{xy}} \\
\Delta_{d_{x^-y^2}}
\end{bmatrix} d_0 \\
\end{bmatrix} \Psi \\
\Delta_f \begin{bmatrix}
d_x \\
d_y
......@@ -360,43 +360,45 @@ presented in the following.
The second column is the basis function in real space, for example, as
the bond pairing on nearest neighbour bonds. The third column is the
two-spin basis function, in terms of the typical superconducting psuedo-
vector formulation $d$. The fourth column is the total
vector formulation $(\Psi, \bvec d)$. The fourth column is the total
spatial and two-spin basis function, calculated as decribed in the text.}
\label{tab:irrep_basis_fns}
\end{table}
The divergent eigenstate will belong to one of the irreps of the point symmetry
group of the lattice (\textit{i.e.} \sym C {6v}).
When the state is a spin singlet or \su, this can be identified by matching the
spacial symmetry behavior with one of the spacial irrep basis functions shown
When the Hamiltonian has an \su 2 spin symmetry, the point symmetry irreps
can be identified by matching the symmetry behavior of the spatial pairing with
one of the spatial irrep basis functions shown
in \cref{tab:irrep_basis_fns}, second column.
If the \su symmetry is broken by the introduction of SOC, the transformation
If the \su 2 symmetry is broken by the introduction of SOC, the transformation
behaviour of the spins under symmetry group operations must be
considered\,\cite{kaba2019}.
Here, the total irrep can be understood only as a combination of
the spatial symmetry and the symmetry behavior of the two spins, \textit{i.e.}
the total symmetry transformation behavior.
To construct appropriate basis functions, we first consider the transformation
Here, the irrep basis functions of the total superconducting state, hereafter
referred to as the \textit{total irrep}, can be understood only as a combination of
the spatial pairing symmetry and the symmetry behavior of the two spins,
\textit{i.e.} the total symmetry transformation behavior.
To construct these basis functions, we first consider the transformation
behavior of a pair of spins under \sym C {6v}. The details of this calculation
can be found in \cref{app:spin_irreps}, the resulting functions are given in
\cref{tab:irrep_basis_fns}, third column.
The total irreps is constructed as the tensor product of the spin-pair and
spatial irreps.
The total irreps basis function are constructed as the tensor product of the
spin-pair and spatial pairing irreps.
We retain only the products that yield physical states, \textit{i.e.} those
which are antisymmetric under exchange of all quantum indices ($E_2 \otimes
E_1$ would yield spacially even spin-triplet pairing and is discarded).
Except for the case $\sym E 1 \otimes \sym E 1$, \todo{what about $E2
\otimes E2$?} either the spacial or the spin-pair space is one-dimensional.
which are antisymmetric under exchange of all quantum indices (\sym E 2 $\otimes$
\sym E 1 would yield spatially even spin-triplet pairing and is discarded).
Except for the case $\sym E 1 \otimes \sym E 1$, either the spacial or the
spin-pair space is one-dimensional.
In those cases, multiplication of the irreps' group characters yields the
total state's characters, and thus the total irrep.
The $\sym E 1 \otimes \sym E 1$ case requires a further decomposition.
This can be done by either forming irrep projection operators for the total
representation, as described in \cref{app:spin_irreps} \todo{Is this actually
in here?}, or by a group theory calculation exploiting the orthogonality of
the group characters \todo{source?}.
representation, in the same way as described for the spin-pair representation
described in \cref{app:spin_irreps}, or by a group theory calculation exploiting
the orthogonality of the group characters \todo{source?}.
Either results in:
\begin{equation}
\sym E 1 \otimes \sym E 1 = \sym A 1 \oplus \sym B 2 \oplus \sym E 2 \, .
......
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