Hey, I am just reading about the drude model and there some things that I dont understand, so I wanted to ask whether somebody could help me out. This are the things I dont understand:
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How does the DC field movement (straight lines between collisions) of electrons in a metal (free electron gas) differ from a AC field movement and when a AC field is applied what does the polarizability means in terms of the drude model. What excalctly is polarized in the free electron space in a AC field?
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How does the dielectric function (AC field) change with the scattering time/free mean?
Hello,
I am having trouble equating two concepts that I have discovered in my studies - the plasma frequency model of permittivity and the Drude model. Highly relevant here is this linked video (timestamped to the appropriate place).
In short, the slide on the video shows that the complex permittivity is given by:
epsilon_cr = epsilon_r - j * sigma / (omega * epsilon_0)
The plasma frequency model is given by:
epsilon_cr = 1 - omega_p^2 / (omega^2 + j * omega * gamma)
Where gamma is the inverse of the relaxation time.
However, when I make all of the substitutions transforming between the two models based on the slides I actually get a plus sign, not a minus sign, for the imaginary component of complex permittivity:
epsilon_cr = epsilon_r + j * sigma / (omega * epsilon_0)
And in some literature I have seen people use the above definitions with the + sign rather than -. What am I missing here? I would greatly appreciate any assistance. Thankyou.
For a magnetic field in the z direction and a periodic time varying electric field in an arbitrary direction, how can an experiment be designed to measure electron mass. Iโm pretty sure n, and q are known. Iโve calculated the resistivity tensor and conductivity tensor. I had to set ฯ to infinity, but Iโm not sure if thatโll help.
So last night Lene Hau's experiment on slow light was pushed to the front page via a TIL. I am a graduate student in her lab and what I read in the comments was a little painful. I'm not at all bothered by those that claim no knowledge of physics and make very amusing comments about light sabers and Bose-Einstein Condensates being the power source for Bose Speakers (that was actually pretty funny). But I was shocked at how many semi-educated people made the claim that:
when light enters matter, it is a bunch of tiny particles that get absorbed and emitted by the atoms randomly. The tiny particles still travel at the speed of light in between the atoms but the path length they follow is now much longer due to the scattering, similar to the Drude model for electrons. This is why light appears to slow down in a higher index material
This is wrong. Very wrong.
Classically it would somehow say that Maxwell's equations require absorption/emission and atomic structure in some way. They do not. A free electron gas still has an index of refraction (so do plasmas and other non atomic systems). Scattering destroys the coherency of light.
Quantum mechanically, the wavefuntion of an incoming "photon" (and I use that word very inappropriately here as all of these measurements use classical laser pulses) is not a "tiny" particle that can travel in between these huge atoms. Typical lasers today generate linewidths on a few hundred KHz, even in the Gaussian limit this leaves photon wavefunction's uncertainty in the k direction VERY large (think meters or km) not picometers. This is a huge misconception and I hope we can, over time, ease people out of it.
This post had noting to do with EIT and or slow light. But I feel like I should also mention that slow light is not "just shining a laser into a dense Bose-Einstein Condensate" as some claimed. BEC's have densities MUCH lower than most solids and the index of refraction inside one is so close to 1 as to make no difference. I can do an /r/physics ama with some other members of the lab if you guys actually want to know more about slow light and EIT.
edit: Thank you all for your responses. I wrote this as a small rant on the misconception and didn't indent to make any claims as the true nature of the light matter interaction (a subject in which I feel comfor
... keep reading on reddit โกI know this isn't a well formulated question, but I'm taking a relatively deep plunge into physics for a job (plasmonics), and it'd be really helpful. What exactly does this Drude Model do, and what can it be used to find about a specific metal?
I'm assuming this metallic permittivity has something to do with the plasmon frequency of the metal (to my understanding, that's the frequency of an electromagnetic field that will excite the free electrons in the metal the most).
I think it is because the electron has a incertainty much smalles than the metal sample, but it doesn't seem right.
I'm reading about the Wigner-Huntington transition to SMH and I'm a high-school senior, so I don't know all that much about density functional theory and such.
http://en.wikipedia.org/wiki/Drude_model
>During its last collision, this electron will have been just as likely to have bounced forward as backward, so all prior contributions to the electron's momentum may be ignored, resulting in the expression
This argument is crucial to be able to use a constant average collision time thorughout time. It means that momentum gained from collisions doesn't accumulate on average and remains 0. Too bad I don't understand this argument.
They are basically saying that for some collision dp=p2 - p1 , p1 is 0 on average thus dp=p. It seems to me that p1 is indeed 0 on average only if you regard the first collision after just turning on the electric field, because then p1 is the momentum before any influence from the field and that was indeed 0 on average. Can someone elaborate a little on this part please?
The argument of saying it is as likely to bounce forward as backward after each collision seems not correct to me. Obviously after a while the electrons start to move in a preferred direction and so one kind of collision will be more likely.
Go post NSFW jokes somewhere else. If I can't tell my kids this joke, then it is not a DAD JOKE.
If you feel it's appropriate to share NSFW jokes with your kids, that's on you. But a real, true dad joke should work for anyone's kid.
Mods... If you exist... Please, stop this madness. Rule #6 should simply not allow NSFW or (wtf) NSFL tags. Also, remember that MINORS browse this subreddit too? Why put that in rule #6, then allow NSFW???
Please consider changing rule #6. I love this sub, but the recent influx of NSFW tagged posts that get all the upvotes, just seem wrong when there are good solid DAD jokes being overlooked because of them.
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A one-dimensional arrangement of single-molecule magnets (SMMs), which are a partially oxidized dysprosium(III) phthalocyaninato double-decker complexes, [DyPc2]Ix, was synthesized in the Communication by Keiichi Katoh, Masahiro Yamashita etโ al. (DOI: 10.1002/anie.202102666) by using electro-oxidation and chemical oxidation. The results of spectrophotometric analysis on [DyPc2]Ix are consistent with the Drude model, which theoretically explains the optical response of the metal. Since conductivity was observed at temperatures lower than the spin blocking temperature (TB), magnetoresistance (MR) effects observed as magnetic hysteresis were observed for the SMM. Our strategy may pave the way for the construction of electro-conductive SMM as spin valves.
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