5 ms·

The article explains that the heat transfer is too great to be explained by the black body radiation for the given temperature. It would be interesting to know

The article explains that the heat transfer is too great to be explained by the black body radiation for the given temperature. It would be interesting to know how they think the heat is being transferred: are the two plates exchanging electrons which are able to quantum tunnel across the gap, or are they trying to say that there's a more fundamental quantum effect going on?

mannykannot 7y ago
It helps to look into the Casimir effect, and in particular the dynamic aspect of it. If I understand correctly, there is a repulsive force on the matter on either side of the gap that is a consequence of vacuum fluctuations within the gap, and I gather that in this case, it is the electromagnetic fluctuations (the formation and dissolution of virtual photons) that is the dominant source (despite this being electromagnetic, it is not black-body radiation from the matter on either side of the gap.) The force is a function of the width of the gap, as virtual photons with a wavelength greater than the gap cannot form, so as the gap narrows, a growing spectrum of photons are excluded, and the repulsive force decreases[1]. Consequently, any motion of one side of the gap results in a varying force on the other. In this case, the motion is from thermal fluctuations, but it could also be the result of sound, so they are also saying sound could travel through a vacuum. Given the difficulty of demonstrating the additional heat flow experimentally, I am skeptical that it will have "profound implications for the design of computer chips and other nanoscale electronic components where heat dissipation is key", at least until we are working at even smaller scales. [1] As the effect is usually presented, with two plates close together, the force on the gap side of the plates is less than that on the open sides, so the net force acts to pull the plates towards one another. https://en.wikipedia.org/wiki/Casimir_effect#Dynamical_Casimir_effect https://en.wikipedia.org/wiki/Casimir_effect#Dynamical_Casim...
- Iv 7y ago
  > at least until we are working at even smaller scales. We are. The current cutting edge for microchip fabs is 7 nanometers and TSMC is planning a 5 nm one for 2020 and a 3 nm one for 2022. And according to wikipedia: "at separations of 10 nm the Casimir effect produces the equivalent of about 1 atmosphere of pressure" they say it is the dominant force on submicron scales between conductors. I don't know where MEMS are nowadays, but understanding this force is probably something that will help them miniaturize even more.
  - Retric 7y ago
    Those nm scales are just marketing at this point, they don’t describe feature sizes.
    - Iv 7y ago
      Oh, I did not know that. Sigh why do journalists accept to go along with these lies? (No, don't answer, that's rhetorical). So apparently feature sizes are around 40 nm even in "7" or "10 nm" processes.
      - mannykannot 7y ago
        Even so, ~1 atmosphere for a gap that is order-of-magnitude comparable to current technology is interesting, and higher than I would have guessed. On reflection, there's a correspondence between the frequency of the light needed in fabricating features of this size by photolithography, and the cut-off frequency for the Casimir effect in those features.
jpmattia 7y ago
It's the latter, ie there's a more fundamental quantum effect going on. The Casimir effect is an effect between two conducting plates separated by only a vacuum. Strange as it may sound, there is a force generated between the two plates which is dependent on the distance between them. My quick take on the article is that phonons cause a microscopic change the distance between the two plates, which allows transmission of phonons across the vacuum gap.

mannykannot 7y ago

It helps to look into the Casimir effect, and in particular the dynamic aspect of it. If I understand correctly, there is a repulsive force on the matter on either side of the gap that is a consequence of vacuum fluctuations within the gap, and I gather that in this case, it is the electromagnetic fluctuations (the formation and dissolution of virtual photons) that is the dominant source (despite this being electromagnetic, it is not black-body radiation from the matter on either side of the gap.) The force is a function of the width of the gap, as virtual photons with a wavelength greater than the gap cannot form, so as the gap narrows, a growing spectrum of photons are excluded, and the repulsive force decreases[1]. Consequently, any motion of one side of the gap results in a varying force on the other. In this case, the motion is from thermal fluctuations, but it could also be the result of sound, so they are also saying sound could travel through a vacuum. Given the difficulty of demonstrating the additional heat flow experimentally, I am skeptical that it will have "profound implications for the design of computer chips and other nanoscale electronic components where heat dissipation is key", at least until we are working at even smaller scales. [1] As the effect is usually presented, with two plates close together, the force on the gap side of the plates is less than that on the open sides, so the net force acts to pull the plates towards one another. https://en.wikipedia.org/wiki/Casimir_effect#Dynamical_Casimir_effect https://en.wikipedia.org/wiki/Casimir_effect#Dynamical_Casim...

Iv 7y ago
> at least until we are working at even smaller scales. We are. The current cutting edge for microchip fabs is 7 nanometers and TSMC is planning a 5 nm one for 2020 and a 3 nm one for 2022. And according to wikipedia: "at separations of 10 nm the Casimir effect produces the equivalent of about 1 atmosphere of pressure" they say it is the dominant force on submicron scales between conductors. I don't know where MEMS are nowadays, but understanding this force is probably something that will help them miniaturize even more.
- Retric 7y ago
  Those nm scales are just marketing at this point, they don’t describe feature sizes.
  - Iv 7y ago
    Oh, I did not know that. Sigh why do journalists accept to go along with these lies? (No, don't answer, that's rhetorical). So apparently feature sizes are around 40 nm even in "7" or "10 nm" processes.
    - mannykannot 7y ago
      Even so, ~1 atmosphere for a gap that is order-of-magnitude comparable to current technology is interesting, and higher than I would have guessed. On reflection, there's a correspondence between the frequency of the light needed in fabricating features of this size by photolithography, and the cut-off frequency for the Casimir effect in those features.

jpmattia 7y ago

It's the latter, ie there's a more fundamental quantum effect going on. The Casimir effect is an effect between two conducting plates separated by only a vacuum. Strange as it may sound, there is a force generated between the two plates which is dependent on the distance between them. My quick take on the article is that phonons cause a microscopic change the distance between the two plates, which allows transmission of phonons across the vacuum gap.