Update theory authored by Philipp Rüssmann's avatar Philipp Rüssmann
...@@ -12,13 +12,13 @@ links: ...@@ -12,13 +12,13 @@ links:
Starting point: Schrödinger equation Starting point: Schrödinger equation
```math ```math
\mathcal{H}\|\psi\rangle = E\|\psi\rangle \mathcal{H}|\psi\rangle = E|\psi\rangle
``` ```
This can formally be written with the Green This can formally be written with the Green
function $`\mathcal{G}`$ as function $`\mathcal{G}`$ as
```math ```math
(\epsilon -\mathcal{H})\mathcal{G}(\epsilon)=1, \quad \epsilon=E+i\delta, (\epsilon -\mathcal{H})\mathcal{G}(\epsilon)=1, \quad \epsilon=E+i\delta,
\quad \delta\>0 \quad \delta>0
``` ```
Thus by knowing the GF one can extract the Thus by knowing the GF one can extract the
systems properties, i.e. the expectation value $`\langle systems properties, i.e. the expectation value $`\langle
...@@ -53,7 +53,7 @@ crystal into three steps: (i) compute the scattering properties of free ...@@ -53,7 +53,7 @@ crystal into three steps: (i) compute the scattering properties of free
Lippmann-Schwinger equation, (ii) construct the multiple scattering via Lippmann-Schwinger equation, (ii) construct the multiple scattering via
the structural Green function from systems geometry and (iii) construct the structural Green function from systems geometry and (iii) construct
the Green from the in (i) obtained wavefunctions and single-site the Green from the in (i) obtained wavefunctions and single-site
$`t$`-matrix and the in thep (ii) computed structural GF. $`t`$-matrix and the in thep (ii) computed structural GF.
### (i) Single-site problem ### (i) Single-site problem
...@@ -115,8 +115,8 @@ positions vanish, i.e. $`\Delta t=0`$. This allows us to embed the ...@@ -115,8 +115,8 @@ positions vanish, i.e. $`\Delta t=0`$. This allows us to embed the
impurity in a finite real space cluster into the host system. The impurity in a finite real space cluster into the host system. The
calculation is then done as follows. calculation is then done as follows.
- Compute the host systems Green function and write out the structural Green function as well as the single-site $`t`$ matrix of the host $`t_{\mathrm{host}}`$. * Compute the host systems Green function and write out the structural Green function as well as the single-site $`t`$ matrix of the host $`t_{\mathrm{host}}`$.
- From the impurity potential compute the $t$-matrix of the impurity and construct $`\Delta t=t_{\mathrm{host}}-t_{\mathrm{imp}}`$ * From the impurity potential compute the $`t`$-matrix of the impurity and construct $`\Delta t=t_{\mathrm{host}}-t_{\mathrm{imp}}`$
- Solve the impurity Dyson equation: $`\underline{\underline{G}}=\underline{\underline{G}}_{\mathrm{host}}+\underline{\underline{G}}_{\mathrm{host}}\Delta t\underline{\underline{G}}`$ * Solve the impurity Dyson equation: $`\underline{\underline{G}}=\underline{\underline{G}}_{\mathrm{host}}+\underline{\underline{G}}_{\mathrm{host}}\Delta t\underline{\underline{G}}`$
- Compute the new impurity potential from the Green function and update the input potential * Compute the new impurity potential from the Green function and update the input potential
- Repeat steps 2.-4. until the impurity potential converges * Repeat steps 2.-4. until the impurity potential converges