Electron-longitudinal acoustic phonon interaction
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The electron-longitudinal acoustic phonon interaction is an interaction that can take place between an electron and a longitudinal acoustic (LA) phonon in a material such as a semiconductor .
Displacement operator of the LA phonon
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Interaction Hamiltonian
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The electron-longitudinal acoustic phonon interaction Hamiltonian is defined as
H
el
{\displaystyle H_{\text{el}}}
H
el
=
D
ac
δ
V
V
=
D
ac
d
i
v
u
(
r
)
{\displaystyle H_{\text{el}}=D_{\text{ac}}{\frac {\delta V}{V}}=D_{\text{ac}}\,\mathop {\rm {div}} \,u(r)}
,
where
D
ac
{\displaystyle D_{\text{ac}}}
is the deformation potential for electron scattering by acoustic phonons .[1]
Inserting the displacement vector to the Hamiltonian results to
H
el
=
D
ac
∑
q
ℏ
2
M
N
ω
q
(
i
e
q
⋅
q
)
[
a
q
e
i
q
⋅
r
−
a
q
†
e
−
i
q
⋅
r
]
{\displaystyle H_{\text{el}}=D_{\text{ac}}\sum _{q}{\sqrt {\frac {\hbar }{2MN\omega _{q}}}}(ie_{q}\cdot q)[a_{q}e^{iq\cdot r}-a_{q}^{\dagger }e^{-iq\cdot r}]}
Scattering probability
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The scattering probability for electrons from
|
k
⟩
{\displaystyle |k\rangle }
to
|
k
′
⟩
{\displaystyle |k'\rangle }
states is
P
(
k
,
k
′
)
=
2
π
ℏ
∣
⟨
k
′
,
q
′
|
H
el
|
k
,
q
⟩
∣
2
δ
[
ε
(
k
′
)
−
ε
(
k
)
∓
ℏ
ω
q
]
{\displaystyle P(k,k')={\frac {2\pi }{\hbar }}\mid \langle k',q'|H_{\text{el}}|\ k,q\rangle \mid ^{2}\delta [\varepsilon (k')-\varepsilon (k)\mp \hbar \omega _{q}]}
=
2
π
ℏ
|
D
ac
∑
q
ℏ
2
M
N
ω
q
(
i
e
q
⋅
q
)
n
q
+
1
2
∓
1
2
1
L
3
∫
d
3
r
u
k
′
∗
(
r
)
u
k
(
r
)
e
i
(
k
−
k
′
±
q
)
⋅
r
|
2
δ
[
ε
(
k
′
)
−
ε
(
k
)
∓
ℏ
ω
q
]
{\displaystyle ={\frac {2\pi }{\hbar }}\left|D_{\text{ac}}\sum _{q}{\sqrt {\frac {\hbar }{2MN\omega _{q}}}}(ie_{q}\cdot q){\sqrt {n_{q}+{\frac {1}{2}}\mp {\frac {1}{2}}}}\,{\frac {1}{L^{3}}}\int d^{3}r\,u_{k'}^{\ast }(r)u_{k}(r)e^{i(k-k'\pm q)\cdot r}\right|^{2}\delta [\varepsilon (k')-\varepsilon (k)\mp \hbar \omega _{q}]}
Replace the integral over the whole space with a summation of unit cell integrations
P
(
k
,
k
′
)
=
2
π
ℏ
(
D
ac
∑
q
ℏ
2
M
N
ω
q
|
q
|
n
q
+
1
2
∓
1
2
I
(
k
,
k
′
)
δ
k
′
,
k
±
q
)
2
δ
[
ε
(
k
′
)
−
ε
(
k
)
∓
ℏ
ω
q
]
,
{\displaystyle P(k,k')={\frac {2\pi }{\hbar }}\left(D_{\text{ac}}\sum _{q}{\sqrt {\frac {\hbar }{2MN\omega _{q}}}}|q|{\sqrt {n_{q}+{\frac {1}{2}}\mp {\frac {1}{2}}}}\,I(k,k')\delta _{k',k\pm q}\right)^{2}\delta [\varepsilon (k')-\varepsilon (k)\mp \hbar \omega _{q}],}
where
I
(
k
,
k
′
)
=
Ω
∫
Ω
d
3
r
u
k
′
∗
(
r
)
u
k
(
r
)
{\displaystyle I(k,k')=\Omega \int _{\Omega }d^{3}r\,u_{k'}^{\ast }(r)u_{k}(r)}
,
Ω
{\displaystyle \Omega }
is the volume of a unit cell .
P
(
k
,
k
′
)
=
{
2
π
ℏ
D
ac
2
ℏ
2
M
N
ω
q
|
q
|
2
n
q
(
k
′
=
k
+
q
;
absorption
)
,
2
π
ℏ
D
ac
2
ℏ
2
M
N
ω
q
|
q
|
2
(
n
q
+
1
)
(
k
′
=
k
−
q
;
emission
)
.
{\displaystyle P(k,k')={\begin{cases}{\frac {2\pi }{\hbar }}D_{\text{ac}}^{2}{\frac {\hbar }{2MN\omega _{q}}}|q|^{2}n_{q}&(k'=k+q;{\text{absorption}}),\\{\frac {2\pi }{\hbar }}D_{\text{ac}}^{2}{\frac {\hbar }{2MN\omega _{q}}}|q|^{2}(n_{q}+1)&(k'=k-q;{\text{emission}}).\end{cases}}}
See also
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Notes
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^
Hamaguchi, Chihiro (2017). Basic Semiconductor Physics . Graduate Texts in Physics (3 ed.). Springer. p. 292. doi :10.1007/978-3-319-66860-4. ISBN 978-3-319-88329-8 .
References
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Hamaguchi, Chihiro (2017). Basic Semiconductor Physics . Graduate Texts in Physics (3 ed.). Springer. pp. 265–363. doi :10.1007/978-3-319-66860-4. ISBN 978-3-319-88329-8 .
Yu, Peter Y.; Cardona, Manuel (2005). Fundamentals of Semiconductors (3rd ed.). Springer.