MM_DEVILS
Joined: 07 Feb 2006
Posts: 16
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 07 Nov 2008 11:38 lorentz model, permeability |
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Hi,
I would like to know, what are Drude and Lorentz models with respect to metamaterials? How can we apply them to derive the constitutive parameters i.e.
ε and µ using these models? Does any one of you have any material regarding these topics?
With Regards,
MM_DEVILS
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rrumpf
Joined: 06 Jul 2007
Posts: 179
Helped: 22
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23 Dec 2008 22:45 material lorentz model |
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Standard materials exhibit permittivity and permeability because of atom and molecular resonances. These can be modeled by a simple mass/spring model called the Lorentz oscillator model. Real material have multiple resonances so the overall behavior is the sum of the all the resonances. A drude model is a special case of a Lorentz model when there is no restoring force. This happens in metals since the electrons are free to move around.
Meta-materials use subwavelength resonant structures to emulate atomic level resonances. The Lorentz model would be fit to some data generated by a more rigorous electromagnetic simulation. Once the fit is done, it could be used to calculate the material properties at any wavelength or frequency.
A left-handed material has a negative permittivity and negative permeability. It was always know that metals can produce a negative permittivity, but it wasn't until recently that negative permeability could be realized. You would want to fit data to the Lorentz models for both permittivity and permeability and then look where both are negative. The negative permittivity is typically realized with continuous metal strips, while negative permeability is typically realized with split ring resonators or loops, but other structures have been shown to provide negative permeability.
Hope this helps!
-Tip
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