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The Straightest Line EVER Measured?! | Quantum Hall Effect Explained

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!