Could a Semiconductor Plate Alter the Casimir Effect?

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Discussion Overview

The discussion centers around the potential implications of using a semiconductor plate in the context of the Casimir Effect, particularly regarding whether a semiconductor's conductivity changes could influence the forces acting on a conducting plate and if this could lead to practical applications such as spacecraft propulsion.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant suggests that the Casimir Effect operates between two closely spaced conducting plates due to photon pressure, and questions how a semiconductor's conductivity might alter this effect.
  • Another participant notes that the conductivity of the semiconductor would depend on various factors such as doping, temperature, and illumination, but argues that the Casimir effect is primarily influenced by macroscopic conductivity.
  • Concerns are raised about momentum conservation in the proposed scenario, with one participant questioning whether momentum could be transferred from external photons to the conducting plate.
  • Further clarification is sought regarding the nature of external photons and their role in the momentum transfer process, with some participants expressing skepticism about the existence of a photon bath that could selectively influence the plates.

Areas of Agreement / Disagreement

Participants express differing views on the implications of using a semiconductor in the Casimir Effect context, particularly regarding momentum conservation and the role of external photons. The discussion remains unresolved with multiple competing perspectives presented.

Contextual Notes

Limitations include the dependence on the specific properties of the semiconductor and the assumptions regarding external photon interactions, which have not been fully explored or defined in the discussion.

Ergatron
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Greetings!

I would love to hear people's thoughts on the following:

My (basic) understanding is that the Casimir Effect acts upon 2 closely spaced parallel conducting plates, because the photon pressure between the plates is less - only wavelengths which are multiples/divisors of the plate spacing can exist.

If one of the plates was in fact a semiconductor, when it ceased to conduct would there be a net force on the (permanently) conducting plate towards the centre of the 2 plates? If the semiconductor were driven on/off at high frequency, could this force become substantial? ( e.g. a potential propulsion for spacecraft )

I haven't been able to find mention of this particular theory on t'interweb - I'm sure there are countless flaws with the theory but I've been out of the physics game for too long now!

thanks in advance
 
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Ergatron said:
Greetings!

I would love to hear people's thoughts on the following:

My (basic) understanding is that the Casimir Effect acts upon 2 closely spaced parallel conducting plates, because the photon pressure between the plates is less - only wavelengths which are multiples/divisors of the plate spacing can exist.

If one of the plates was in fact a semiconductor, when it ceased to conduct would there be a net force on the (permanently) conducting plate towards the centre of the 2 plates? If the semiconductor were driven on/off at high frequency, could this force become substantial? ( e.g. a potential propulsion for spacecraft )

I haven't been able to find mention of this particular theory on t'interweb - I'm sure there are countless flaws with the theory but I've been out of the physics game for too long now!

thanks in advance

The Casmir force would be determined by the conductivity of the semiconductor. The conductivity of the semiconductor would depend on how it was doped, the temperature of the semiconductor, whether it was illuminated, and other microscopic details. However, the Casmir effect wouldn't be sensitive to the microscopic details. The Casmir effect would only be affected by the macroscopic (i.e., average) conductivity.
 
Besides, what you are describing does not conserve momentum.
 
OK, thanks - but wouldn't the momentum be taken from the external photons?
 
What external photons?
 
The radiation pressure acting on the permanently conducting plate towards the midpoint - if there wasn't a matching force the other side of it, wouldn't momentum be transferred from the photons comprising the radiation into the momentum of the plate?
 
I don't think you are understanding this. It's not like there is a real bath of photons out there that can somehow be shielded if going from the left but not if going from the right.
 

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