- #1
BlackHole213
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I originally posted the following question on physics.stackexchange, but no one was able to answer it. I did find this answer on PhysicsForums, but I was already aware of the oscillation of electrons in response to an external electric field.
What is the physical cause behind a material having a negative real part of its dielectric function? Given the complex permittivity, \epsilon(\omega)=\epsilon(\omega)'+i\epsilon(\omega)'', the Drude model gives
\begin{align}
\epsilon'=1-\frac{\omega_{P}^2}{\omega^2+\omega_{\tau}^2}
\end{align}
where \omega is the frequency of the incoming light, \omega_{P}=\sqrt{\frac{Ne^2}{m\epsilon_0}}is the plasma frequency, N is the electron density, m is the electron's mass, e is the electronic charge, and \omega_{\tau} is the frequency of collisions between conduction electrons and the ion lattice.
If \omega is small enough, then \epsilon'<0. But this is just the mathematics behind negative permittivity. How does it physically happen?
What is the physical cause behind a material having a negative real part of its dielectric function? Given the complex permittivity, \epsilon(\omega)=\epsilon(\omega)'+i\epsilon(\omega)'', the Drude model gives
\begin{align}
\epsilon'=1-\frac{\omega_{P}^2}{\omega^2+\omega_{\tau}^2}
\end{align}
where \omega is the frequency of the incoming light, \omega_{P}=\sqrt{\frac{Ne^2}{m\epsilon_0}}is the plasma frequency, N is the electron density, m is the electron's mass, e is the electronic charge, and \omega_{\tau} is the frequency of collisions between conduction electrons and the ion lattice.
If \omega is small enough, then \epsilon'<0. But this is just the mathematics behind negative permittivity. How does it physically happen?
