Lecture 22: Metals, Insulators, and Semiconductors

[@qwertycorno]

Lecture starts at 38:09. Entanglement starts at 1:04:02.

[@LydellAaron]

1:00 physical significance of the crystal momentum 10:10 crystal momentum derives from the same momentum concept of an object which is under uniform circular motion in centripetal acceleration.

[@suzieanddusty]

Totally in love with Allan Adam's way of teaching and this course.:D

[@lakshithalathpandura4579]

21:32 It should be q=q0 + N (2π/L); It is meaningful If I say q=q0 + K ; K is the reciprocal vector which is N (2π/L) in 1-D

[@melcochaguzman2694]

one of the best expanations about crystal quamtum I've seen. Nicely done

[@andrewhobbs255]

Teacher: Did that answer your question? Student: Yes and made more questions but thanks.

[@benjaminmorris6714]

I was directed to this video in my philosophical research, and I was quite impressed with this video. I have pretty much zero foundation in the topics discussed, but the professor explained them in a way that I was able to follow along and find the answers I sought (and then some). His clear and concise explanation of the concepts themselves compensated in large part for my lack of understanding of the actual mathematics. Thank you for making this available!

[@rijumondal6876]

mit thanks for saving my exam !!!!! you guys truly signifies holistic education!!!!!

[@BijayPuriphysicsist]

it's like the best thing you can ever do, if you wanted to be shiny, fluttery flying thing. .. awesome lecture..

[@waqasriaz4163]

MIT IS world number 1 for reason👍👍

[@kenanfyi]

OMG this is amazing how he explains that the diamond is transparent because the required gap for the electron to jump the state is so huge that the light does not have enough energy to do that so it stays transparent.

[@AliReza-cx7wg]

What is momentum in Quantum mechanics? answer: Momentum is a concept and property from classical physics. It describes a single particle and as we know from classical mechanics we can attribute a plane wave to a free particle with a constant velocity. However, in quantum mechanics for bound systems like electrons in Atoms, Molecules, "solids" we have localized electron that the potential they experience around themselves dictates their position. therefore we can add up a large number of plane waves with different momentum to find a localized function that describe electron in a specific potential. Now momentum is not a good quantum number but gives some information about the symmetry of the wave function.

[@indiaview9414]

Before attaining this lecture you need to do homework over Crystallography, Eigen values, Schrodinger's equation and bra ket notations significance.....

[@heroncortizo1993]

"Physics is an aesthetic as well as intellectual pursuit." :-)

[@Tala-qj6tz]

At 21:32 I guess Prof Adams meant q=q0+N (2*pi/L)

[@t_a7923]

Why are crystals transparent at lower frequencies??

[@lakshithalathpandura4579]

Yes. I also felt the same q=q0 + K ; K is reciprocal vector which is N (2π/L) in 1-D

[@byronwatkins2565]

I do wish you had explained how excited semiconductor electrons leave behind charged holes and how the "negative mass" of the electrons at the top of the valence band leads to holes acting like positive particles. I also wish you had mentioned that Drude's model applied to a wave packet means that any one of the eigenstates in the packet can be scattered by phonons, defects, or impurities at any time and lead to terminal velocity.

[@kisho2679]

could the properties of "Rare Earth Elements" replace the technological usage of "Metals, Insulators and Semiconductors"?

[@t_a7923]

@39:55 why are the upper bands much wider than lower ones????? is that bcoz when we build a periodic lattice the outer electrons are more prone to perturbations from that of neighbouring atoms..

[@volcanic3104]

1:40 Are x0 and p0 constants? How can = constant if =/= 0??

[@forfun5140]

41:07 Why does superposition make expectation value of position change in time?

[@santiagoarce5672]

Electrons move around in real life right (most of the time)? But electrons in energy eigenstates do are not moving (the expectation value isn't changing), which is why they're also called stationary states. States in which an electron's expected position can change are not eigenstates, and are thus a superposition of energy eigenstates.

[@MichaelSchlegel-xd1qs]

Why are wide-gap semiconductors not transparent? (You know because they also have a large band gap just like the transp)

[@ianprivate3626]

Germanium is transparent to infra red light.

[@STEM671]

ENERGY STATE , CHARGE POLARITY ; VARIATION IN VOLTAGE IN 3D CRYSTAL ;

[@scottkleyla7752]

Oh this tickles my interest/fascination with "ENTANGLEMENT" and unknown possibility.

[@thenarratorfromsultanpur]

i need a lectures on plasma physics where can i find it

[@TheEmptyForever]

Amazing lectures! Thank you very much!

[@ashlynnundlall]

Which course is on special and general relativity? I've done this one

[@IliaToli]

Just go to the website, ocw.mit.edu/. There you find all kinds of classes, by the name. BTW, I intend to listen also the third course in the topic. It appears to not be here, but yes on Yale.

[@ashlynnundlall]

Thanks

[@correa95100]

what book can I read to understand better this theme?

[@mitocw]

In this case... books. From the Readings section of the course: [E&R] = Eisberg, Robert M., and Robert Resnick. Quantum Physics of Atoms, Molecules, Solids, Nuclei, and Particles. Wiley, 1985. ISBN: 9780471873730. [Li.] = Liboff, Richard L. Introductory Quantum Mechanics. Addison Wesley, 2002. ISBN: 9780805387148. [Ga.] = Gasiorowicz, Stephen. Quantum Physics. John Wiley & Sons, 2003. ISBN: 9780471429456. [Sh.] = Shankar, Ramamurti. Principles of Quantum Mechanics. Springer, 2008. ISBN: 9780306447907. [E&R] Chapter 13: Sec. 1-7. [Li.] Chapter 8: Sec. 1-4. [Ga.] Chapter 4: supplements; Chapter 13: all. [Sh.] see Liboff See the course on MIT OpenCourseWare for more information and details at: ocw.mit.edu/8-04S13. Best wishes on your studies!

[@sonarbangla8711]

I think Susskind is right gravity and QM are one and the same thing, what is left to do is to devise how unitary evolution of classical from the quantum, called a more complete formulation by Einstein is required. Maldacena's conjecture about QC probably provide coherence/determinism, is what is needed. Susskind did provide a rudimentary finite gate quantum circuit, physics need to follow it up.

[@schmetterling4477]

Nope. :-)

[@not_amanullah]

This is helpful ❤️🤍

[@raybroomall8383]

Why I'd 'P' used as a probability in previous lectures and then as a moment.

[@shibaneethakur5035]

As per your description crystal in 1D called as insulator and in 3D called as metal.... 🤔🤔🤔🤔🤔

[@prasadpawar7027]

I guess insulators only depend on parameter L.

[@not_amanullah]

Thanks ❤️🤍

[@mfoucault1984]

If he is talking about nearly free electrons, those from Bloch theorem, he shouldn't be plotting the bound energies.. he is like mixing tight-binding and weak potential approximations.. this is happening from lect 20..

[@t_a7923]

Why are crystals transparent at lower frequencies?

[@forfun5140]

because at lower frequency, the energy of the light is not enough to excite electron in crystal to another state

[@t_a7923]

@@forfun5140 does that mean that at high frequency the e are excited and they emit radiations in visible region making them nontransparent or giving different colors to the crystals. tysm for the rply❤

[@davidwilkie9551]

Question, why, if by the mathematical projection of potential physical forms, it is possible to emulate the functional phenomena of materials and instrumental devices, then actual mechanism of continuous cause-effect is "known" in a practical sense, by degrees of correlation. Ie the zero-infinity difference of unity-tangency to No-thing is the basis of flat space ground state and balanced symmetrical curvatures of Neutronic properties.., AdS/CFT Quantum-fields style and orbital boundaries, horizons etc manifested in/of time duration timing QM-TIMESPACE Superspin Modulation positioning by logarithmic condensation in e-Pi-i sync-duration function. (Ie review and reiterate the systematic misnomers of aquired identifiers/jargon. At least use SI Units?) All information is temporal, "sound" symbolic perceptions that "ring true" are Theoretical until observable in Actuality, or are basically "mystical" fantasy.., great care is required to observe an appropriate Dimensional Analysis, in which scalar proportioning is not misaligned with the re-presentation of timing concepts.., which is why Mathematics exists, to test Reality. Agreed, as in this lecture, the type of coordinate system symbolism used "doesn't matter" except for AM-FM alignment and correspondence with the objective. Polar Trigonometry and Axial-tangential Cartesian/Pythagorean terminology are basicly twoness aspects of real-time logarithmic singularity location condensation connectivity.., the same context. The general caution to "think for yourself" but "don't believe what you think", applies to the "authority" problem of becoming attached to your habits of thought. The observation that it takes 20X longer to rethink a strategy or technique is why Theorists are prone to destroying hands on experiments, we should never trust metastable pulsed states of being, particularly when associated with political expediency. The idea that the name or symbol is the thing, is Magical Thinking Fast and Slow.., prone to fantasy andentertainment, or testable Mathemagical theory and serendipity. Opposite thinking is occasionally also centering, so Einstein did not want to hear Bergson for whatever reason and that blocked out the all prevailing fact of time duration timing, learnt by embedded inclusion by everyone. Rigorous or Religious emphasis on particular concepts can bias proper interpretation away from ordinary experiences, and in a World where 1+1=2 is conditional relative to logarithmic singularity planes of existence in QM-TIMESPACE, the dominant shared belief is crucial. "Not even wrong" is the Theoretical ideal of WYSIWYG physics Observation.

[@gordtvradio3465]

Allan reminds me of Mac from Its Always Sunny

[@Blacklunaproductions]

The guest after the lecture had no idea what he wanted to say

[@pertedium603]

That guest speaker at the end was a complete disaster. He tried to conduct a 'show and tell' and failed utterly. I gave myself a math test on the internet the other day and am probably capable at the 5th grade level. (That's not supposed to be funny, but maybe it is.) Nonetheless, I've watched this entire series (up to 22), based solely on the interest generated by a book written on Albert Einstein. It's called 'Einstein'; - by Walter Isaacson. (He also wrote a biography about the life of Steve Jobs.) Many, many physics books that deal with quantum mechanics are written for non-physicists, non-mathematicians, non-scientists etc., and they are entirely comprehensive within particular parameters. Books by Stephen Hawking, Brian Greene, Michio Kaku, Roland Omnes, and others. For someone to have researched and written a book and then offer a presentation that was supposed to have some knowledge and depth, this guy was such a disappointment. Using 'CC' shows how incoherent he was. He says himself, "For this hand-waving." And more, what the hell does a 'Flying Spaghetti Monster' have to do with anything anyway? The mouse, on the other hand...was actually interesting.

[@ariadne4720]

I agree completely, I was going to publish a comment myself and you did already ;) I loved Isaacson's book on Einstein, so much so I will definitely read it again

[@C-BAS]

i keep on ending up in this series after falling asleap in my chair with autoplay on and somehow i will end up here. i understand NOTHING.

[@vasugoel27]

Umm... Can't we get the footage of office hours😅😂

[@ruby-oo9fi]

Indians : exist Walter Lewin: It's free real estate

[@ianprivate3626]

Waltzing psi-tilde...

[@stefanbauer297]

Sorry, but Mr.Levinsons contribution to EPR is poor, confusing and not helpfull! By the way: he doesn't know when Einstein died!? The whole item of entanglement, etc. would have deserved a lecture of its own! By the way: why not spell "Schroedinger"(instead of Schrodinger), that would come next to his German name!

[@schmetterling4477]

Entanglement is boring. There is no there, there.

[@johnnyyang7492]

UR……

[@SimakSantana]

this kind of physics is so boring lol