The Straightest Line EVER Measured?! | Quantum Hall Effect Explained
HTML-код
- Опубликовано: 21 сен 2019
- Can you find a line that's straighter than this one?
Hey guys, I'm back with another video! This one's a long one, and in this video I discuss what I believe to be the straightest line that's ever been measured in a science experiment. I'm sure there are examples of even straighter lines, but let's chat about this one anyway because it's so cool.
The measured data is for a phenomenon known as the Quantum Hall Effect, named after Edwin hall who discovered the original (classical) Hall Effect. The Classical Hall Effect works on the idea that electrons moving along a length of a strip of metal (i.e. as part of a current flow) will be diverted towards one of the sides of the strip of metal if the strip is placed in a magnetic field perpendicular to the initial current flow. The idea is that as we increase the strength of the magnetic field, we expect the electrons to be pulled more to one side of the strip, thus changing the voltage in the transverse direction of the strip.
However, this is not what we see. Initially, for small magnetic field strengths, what we expect to happen does happen. But for large magnetic field strengths, we see big plateaus - as we change the magnetic field, the electrons don't seem to be any more pushed to one side of the strip for a big range of magnetic field strengths, until suddenly they jump to being pushed to one side a lot more than they were before. This manifests itself in a very VERY constant transverse resistance over a large range of magnetic field strengths. These constant resistances have been measured to be constant to within one part in 1 BILLION! And this experiment was done with a rough sample that wasn't perfect by any means. Hence, these constant resistance values along the plateaus of the graph are known as Topological Quantum Numbers - the resistance values are exactly constant regardless of how we modify / damage / mend the sample, which is mindboggling.
Also, these constant resistance values are what I think make the straightest lines ever measured. As we mentioned already, along these lines the resistance values are identical to within 1 part in 1 billion to resistance values measured for different field strengths.
I try to make this behaviour a bit more understandable by discussing how electrons, when transitioning between energy levels in an atom, can only do so by absorbing photons of a very specific energy. If the energy of the photon is too low or too high, it will not interact with the electron and the
So I hope you enjoy the video! If you want to watch some of my vlogs (yes I'm vlogging again!) then check out my Instagram @parthvlogs. Subscribe here for more fun physics content!
Dots: found extremely close to each other
Physicists: they're straight, they're just good friends
bruh
For the flow of electrons , the left-hand rule can be applied. Accordingly, the Lorentz-Force, acting on the electrons, points to the left.
Your channel is one of the few gems on this platform and I really appreciate your work. Your explanations are easy to digest and very simple to understand. Please keep up the good work :)
Hey Parth, I stumbled across your channel a few days back and have binge watched a lot of your videos. They are all fantastic, and detailed for all levels. Keep up the awesome work, we love them. Would you be able to do some videos on the physics behind semiconductors? (It's my 3rd year physics unit)
I hope to see you at 1 mil in no time at all dude. Love your work :))))
I can definitely see your channel growing into a big 10M science channel in future. Keep up the good work!
Nice video dude, simple and very well explained! keep up with the good work!
another great video. i've 'known' about the hall effect and its many applications but never knew about the quantum hall effect and the world's straightest line. thanks for your video! i learned something new!
Since you are already halfway there (on the Quantum Hall effect), I'd love it if you could expand into coverage of how "Exploring 4D quantum Hall physics with a 2D topological charge pump" by Lohse, Schweizer, Price, Zilberberg, and Bloch in January 2018 Nature 'proves' the existence of a fourth spatial dimension.
Hey Parth I loved your video on one of Maxwell's equations. I was wondering, could you make a video that looks at "Why does gravity slow down time?" I sort of get why time slows down for moving things, but can't seem to get gravity's relationship with time at all really. Your insights will be huge!
One small correction. By convention (and due to interesting historical misconceptions) current flow is opposite to the direction of electron flow. Otherwise a pretty decent explanation - thanks :)
Agreed it flows opposite to the flow of electrons.
You are right buddy , I have studied Maxwell's equations for soo many years but still something new comes up whenever I see them and still learning from that . Thanks for the video. Please make a video on quantum spin hall effect
Thank you for this video. It cleared my understanding of Quantum Hall Effect
What’s sometimes amazing about quantum mechanics is whether studying condensed matter or high energy how some of the most accurate measurements always end up coming from these fields. It’s like the most empirically well verified field of science. Yet it is impossible to build any sense of human intuition about its most fundamental structures.
Hi Parth you explain things really well. Great videos. Thanks!
You have the same issue I do... try getting non-reflective coating on your next pair of glasses :) Nice vids btw! Keep up the awesome work.
Excellent videos Parth 👍👍👍👍
Thanks! This was quite clear and easy to understand! Much appreciated.
Nice video ! It would be great if you make videos on concepts like breaking time reversal symmetry, Quantum spin hall effect !
Beautifully explained: so clear!
Keep up your marvellous work man
Wow!. You explained it so well. I wish I had a teacher who could explain concepts like you.Thank you.
Thanks for this video. Quite interesting (I didn't know the Hall effect). But, one question, one comment, one suggestion:
Q) How can be a "Hall resistance" measured, as there is no trasversal flow of current in the metal plate? In other words, as the electrons tend to adhere to the right side (in the example) of the plate while flowing, their movement is still longitudinal. So, apparently there is a "Hall voltage" but no "Hall current", which leaves "Hall resistance" without much sense.
C) AFAIU (..U is for "understand"), the line is straight because... nothing happens. The photons have not the right energy, so are not absorbed and that's it. It's like (just a stupid example to clarify the concept) measuring charge density in the vacuum of space in time. It's zero, and so remains. Perfect straight line as well.
S) I don't know if you are aware, but in your videos there is a red light ring reflex on your eyeglasses (probably due to the camera). My suggestion is to remove this, a bit spooky, "ParthG effect"... ;-).
Bye and, again, thanks for your videos.
Hey, been enjoying your videos! I'm in a dilemma between choosing A levels for natural sciences or for medicine and was wondering what kinds of actual physics based jobs would be available if I specialised in physics/astrophysics. Is research restricted to only those who graduate with the best degree, making it a harder goal to aim for, or is it more achievable than people make it seem?
Sometimes I forget how counterintuitive quantum mechanics seems to be! Great video, and I could not think of a straighter line :D
4:12 The force is reversed. The direction shown in the diagram is for a POSITIVE charge moving through a magnetic field, but electrons are negatively charged so the force is to the left not the right. One other very important point, we always say current flows from positive to negative when in reality electrons flow the opposite way. So, he also has the current flowing the wrong way.
Thanks for this physics channel
Keep doing lots and lots of videos in physics
Nicely explained Parth
very good explanation for a complex phenomena that has quite frequent implications on everyday life
Wonderful explanation!!!
Excellent video! And personally charming.
Keep up the good work!!!
The perfect straightness just proves that despite how impure the universe is, energy in itself and the gaps associated with it are simply pure
Great video think you , Can you talk about quantum hall spin effect ?!
Great video Parth!
But wait, this explanation is based on Bohr's theory which ascertains fixed orbits as the paths of electrons around the nucleus. Yet now, we know that there are no fixed orbits but rather orbitals and positions of electrons are based on probability. So, is there an explanation that accounts for the Quantum theory or there's only this one?
Indeed, if the position is a probability, so should be the energy of that electron and each of the various "plateaux" would also a region, with a vertical thickness, from its probabilistic origin, not a pure line, isn't it?
bruh, the energy is quantized. even by schrodinger equation
came for looking explanation of quantum hall effect, got probably the best explanation of Hall effect as bonus
Hey Parth, I love your videos and this one is helping me on a school-project. At 4:00 you saied that the force (Lorentz-Force to my Knowledge) makes the electron curve to the right. When i use my Left hand and point my thumb in the direction of the electronflow and my indexfinger show the magneticfield then the force should make the electron curve left. I am slightly confused, and would love any kind of explanation.
beautiful explanation
It went so smooth, amazing
lovely explanation. more!
Amazing explanation 🤯🤯👍👏👏......
Hi! I love your videos. You make simple concepts vary easy. Congrats! So, I have a quenstion to you. I often send to my friends the following sentence: May the mass times the second derivative of space with respect to time be ever in your favour. This is a sophisticated way to say May the Force be with you. So, is this correct?
The mirrors made for the LIGO detector have an average surface roughness of (roughly) a billionth of their diameter so their cross section might be as straight a line. Interestingly while I could not find any direct evidence for it (despite looking for it) the only way for them to know that those mirrors are that flat (and therefore straight) is if they have a reference optical flat that is even flatter. So that may do it: a physical object flatter than an observed mathematical flatness (although it might not be too hard for them to make a more precise measurement whereas making a flatter mirror of that size may be impossible). Smaller, even flatter, surfaces can be made by shearing crystals apart and getting near atomically perfect surfaces but because they are smaller they may not actually be "straighter". I also learned quite a bit from this video and your pair of Maxwell's equations videos Thank You.
I m stunned....mesmerising explanation
Nice presentation.
This is awesome! For another nomination for straightest thing ever, I'd choose LIGO.
Great video, thanks! Just one question please: although during flat line period there is no jumping of electrons from orbit to orbit, increase of total energy of the system definitely rises (magnetic field gets stronger). What is a manifestation of such increase, having in mind that there is no voltage change in the plate? In other words, where the surplus of energy goes? Does temperature goes up even during periods of time when resistance remains the same?
If the magnetic field does no work, no energy is exchanged.
Is the direction of magnetic force consistent with right hand rule (fingers = B field , thumb = v vel. and palm = force ) in case of positively charged particle ?
Parth let me ask a question. Given that experiment ¿what you think would've happened if researchers increased energy to the point of getting to i=0?
May your enthusiasm live long and prosper.
The fact that we observe plateaux and not discrete quantized points is actually due to the samples being dirty with many impurities is what makes the QHE really awesome to me.
I have studied Hall effect during my high school course but didn't have the resources to plot the graph experimentally. I thought, there is linear relationship between Hall resistance and magnetic field throughout the graph plane. But never searched it online.
Parth, you totally rock! You should consider teaching. Love your videos!
Hey Parth. Thanks for such a great video. Just a quick question. If an electron absorbs a photon with an energy that is too high can it still exite to a higher orbital but travel in the orbital with a greater velocity?
@Jerry L Kreps does that mean that electrons in a specific orbital always have a specific (discrete) velocity as well
6:30 You mention a "hall resistance". So is this like if an electron tried to go back to the positive side of the plate it would experience a lot of difficulty & would have to spend a lot of energy to get back?
You are amazing please keep it up
Love this video. I am still trying to understand the connection between the increasing magnetic field and the "creation" of a photon. How is the photon created that ultimately excites the electron to a higher energy level? Is the increasing magnetic field associated with the increasing electric field across the strip of metal in some way creating photons? I need to see down this rabbit hole!
The force on negative (electron) charges point the other way. The magnetic field (a pseudovector) distinguishes positive from negative charge carriers. Otherwise, we can pretend that all currents are due to positive charges.
Hall effect and quantum hall effects are the only found in metals or it can be found in semiconductor and insulators???
Great, Great, really great....please keep going....
Che cosa succede se il campo magnetico che attraversa la striscia, ruota di 90° puoi spiegare grazie.
Is it enough for quantum hall effect?
what about the graph of latent heat?
while we keep on increasing the temperature the state converstion makes it constant which i also a straight line though...
BTW love your work:)
love from your origin.........
Oh wow. You are trying to do what I hoped I'd start doing one day. Bring out physics experiments and theories and get away from the technically incorrect and trying to solve for the real complicated aspect of it. Basically you ain't showcasing pop-science but showcasing roughly what gets presented in undergrad physics classrooms!
I should start doing this after I finish studying too!
Great Content.
Amazing vid Parth! Tho why dont we talk about transverse current while considering the transverse voltage? It kinda doesnt make sense how the equations are set up here. Thanks already!
Could you build from here to the A-B effect?
Amazing Bro..
Hello Sir, can you teach us just the basic of calculus plss we really need it
The Quantum Hall Effect at the level of atoms is identical to what is observed when we add heat to water (H20). As we increase the temperature of the water, the state of the water changes from liquid to steam at a specific temperature. If we lower the temperature of the water, the state of the water changes from liquid to ice at a specific temperature. So even though we may be changing the temperature at a constant rate of change, the state of H20 remains constant until it reaches specific temperatures. So graphing the state of H20 versus temperature with the state on the vertical (ice at 0, liquid at 1, and steam at 2), we get a horizontal line for any change in temperature and from one state to the other, and a vertical line at the point where the state of H2O changes. Like a stair step. This is an experiment that you can do on a stove top with a thermometer and a pot with a glass lid - no fancy science apparatus required. Although, in practice you will be changing the temperature in steps and you have to patient to observe when the steam first appears in the underside of the glass lid. The fancy science apparatus is required to get more accurate measurements.
Great vids ! Any about the "real meaning" of the spin of particles ? And I would guess that the trajectory of a a neutrino might very well be the straightest line in the Universe... Not yet measured, though, as far as I know.
Please make some videos on landau levels
Hello bahiya..I was just thinking that of we could study the planes that all of the planets move in and see if they resemble a cone(coz that's what it looks like in the classic spandex thing that is sued to demonstrate gravity) with the sun at the Apex...would that be a sign for the existence of the space time....and yeah you're the best☺️
And wouldn't the electron eventually throw off a photon and bump down to the lower energy shell if it doesn't encounter a photon or another atom? Trying to make sure I understand this.
I think there is a slight mistake at 3:58 , the force needs to point to the left.
If you take the Magnetic Force, which is F = q(v x B), then the force you drew in the video would be correct if the particle was positively charged. But in this case, there are electrons which have negative charge.
@Essence of Calculus Yes the Fleming Left hand rule is for positively charged particle, so for negative charges like electron it will go left.
Great video. (You need to know the Mysterons are stalking your room)
Hahah :D
awesome!
You hav said that quantum Hall effect observed for high magnetic field but I googled it n it says it is observed at very low temp magnetic field not any restriction
Two things:
- Impurities in the copper strip? Is the Rh vs B curve really independent of the atoms themselves? I would have thought that the energy for the electrons would be somehow dependent of the atom, and thus, that the proportion of impurities would matter.
- If the plateau were so "neat", would it not be that the transitions would be purely vertical? Right now, from i=5 and i=6 you need B varying from 5.5 to 6T. In electronic, we would call it the "raise time". And that raise time curve is more like an S, so it either enter smoothly in the plateau area, but the, where does it ceases to be part of the S and becomes part of a straight line? So, how "far" have we to be from the transitions to really be on a straight line?
And by billion, you mean 10^9 or 10^12? (short scale or long scale ?) Even with 10^9, than means what, nanoOhm precision for Rh ? We can measure that? Or making the same experiment a second time, the curve that we get, the second time, is EXACTLY the same as the first one, redrawing over the first one, with a pixelization better than 1 in 10^9? That seems like an Olympic exploit all by itself.
And a third thing: if the edges of the strip were like a saw tooth zig-zag, the Vh value would probably differ, isn't it? Same, somehow, if the strip is more a trapezoid than a rectangle. So, how can we be really sure that the plateaux are really "straight lines", given that they could vary (Rh would) with the form of the copper strip?
Bhaiya, please maje video on stimulated emission!!
please explain the Quantum Hall effect :)
If electrons do not move even when higher energy photon is applied, then, how can we ionize atoms with the help of radiation?
so the hall effect is basically when electrons move through a piece of metal and meet a magnetic field, they get moved to a side which makes one side positive and the other side negative?
The video is very interesting and I enjoyed it. However, in the title of the video, "Quantum Hall Effect Explained" part is misleading.
Yo made a mistake, according to Fleming's Left Hand Rule the force experienced by the charge particle should be inward not outward because the direction of current is considered not the direction of flow of charges.
yep, I hope he can edit this!
I think you are incorrect. Electrons are moving from - to +.
The Lorentz force is F=e*v x B.
So with your right hand:
- thumb -> direction of the electrons velocity
- index finger -> magnetic field direction
- middle finger -> force direction
Hey, your awesome, I was looking for equation of this virus I know we can defeat all virus and I want my mind to see it in equation can you help me please
When one say the maths is quite complicated, that means he himself don't know it...I always do that when I have to talk about something that I dont understand properly ...PS great videos to understand physics
Thanks a lot for this great and clear explanation.
I didn't get something. Why is there a one part in billion difference in the results? I have some ideas but I'm not sure whether they are correct or not:
Maybe it's the effect of quantum fluctuations.
Maybe particles coming from the outer space hit the metal.
Maybe there are some other environmental effects, which I have no clue what they are.
Maybe the measurement instrument is causing an error (which doesn't seem so based on the explanations in the video)
I'd be grateful if you answer my question.
Thanks again :)
Best guess would be impurities in the metal.
Wow ! So you are suggesting that the resistance remains so perfectly constant (measured to a billionth !) while the magnetic field changes during certain quantum Hall effect steps ! Amazing how you expressed your experiences as an undergraduate, that I could relate to 100%. Had some issues with the thermodynamics due to a very boring sounding Prof. Thinking back, that would have been so exciting if a different guy were giving the lectures...Surely you will get similarly super straight lines if you were to repeat the photoelectric effect (Einstein's prize winning experiment !) - lets say plot photon intensity (of course with variable frequencies) against the number of electrons leaving an homogenous metal surface..., no ?
If you enjoy this line of thinking I recommend checking out the channel “Sharkee”, where he asks about ‘what is the most massive thing in the universe’ etc. from an informed physics perspective.
More electromagnetism videos plz. :D
11:15 An orbital is NOT an electron shell. Orbitals are volumes of space within each shell where the probability of finding an electron is greater, or as we call them electron clouds. They can be thought of as 3-dimensional harmonics, whose shapes are determined by solutions to the Schrödinger Wave Equation.
Can these "lines" be taken advantage of, in some kind of lab standard?
I suppose the value we measure, when we increase the magnetic field, is the V hall (voltage hall), this is THE important value in that experiment. So why do we infer the R Hall with the Intensity and draw the graph ?... In other word, why don't we draw the graph directly with the V hall & the magnetic field ? What is the interest of doing that "step forward" ? By the way, thanks for the video ! 😊
Am I sensing another R Feynman in the horizon? Well done Parth, keep it up 🙏
That's gotta be the best compliment he has ever received!
sir would you like to review a perpetual motion device proposed by me ?
it would really be helpful 😊
plz do reply
Please finish Maxwell equation and their solution
For those who are confused with the direction of deflection of electrons, it is the opposite to what's shown here. Parth probably wanted to keep things simple as possible.
Hi. The Hall effect is used in modern Flightsim Joysticks as a selling point....
They claim nothing touch's anything therefore more accurate and sensitive.
I really enjoy your videos...keep up the great work. Cheers
At the first part of videos, the direction of Hall Voltage will be in opposite direction as charge of electron in negative!
Disorder is not only desired, but constitutional for the QHE. The QHE wouldn't exist without disorder in a material.
What you mean straightest? How about supercurrent in josephson junction or shapiro steps which are also obtained for josephson junctions? Or Coulomb blockade which is also perfectly straight?? That's misleading.