As a research student starting to learn topology, this video actually gave me some useful intuition that is difficult to acquire from purely equation point of view. Thanks for the great materials. Appreciate much hope to see more from you!
a vtuber explaining high level Physics. i had only imagined it but you are actually out here doing it. i have to say your 3D model is very well done with hand movement and everything.
I loved the videos. You have explained them so simply that, for beginners, it is an optimistic start point. But in this video, I could not help noticing the graphene structure to be written wrong. Keep making such videos.
Could you do a video on time reversal symmetry breaking and what it means? And how are states of matter classified according to the symmetry they break!
Hi, awesome video! One important case you didn't address is spin-orbit coupling which spontaneously breaks time reversal symmetry without any giant external field or twist. Sure most materials don't show high enough S-O interactions but some actually do, resulting in a "native" non-zero berry curvature
i realize that this is advanced stuff and digging into the literature is probably best than to just relying one one 15 minute video, but there are things i still find difficult to grasp about Berry curvature: 1. Is Berry curvature the property of one electron in a material, or does it involve the whole bulk? is it a function of position (and time (?)), or does it have constant value throughout? 2. Being derived from schrodinger's equation, is Berry curvature a general property of solids? does every solid crystal have it, just in most of them the effects are trivial, or can it be defined only in certain classes of materials? 3. Is the finite value of Berry curvature in a material considered a thermodynamic phase? do you need to cross certain value of pressure and temperature to get this effect or is it "on" all the time? 4. From what i understand about magnetic field and circular motion, when an electron orbits around a magnetic field, aside from its position its momentum also "orbits" in the same way (the x and y components of position are sinusoidal cos() and sin(), and both are phase-shifted 90 degrees for momentum x and y components). If Berry curvature makes orbit in momentum space, does that induce circular motion in electron position also, producing a magnetic field? do magnetic field and Berry curvature couple to each other? 5. What happens if positive charge carriers (like holes) are involved? can Berry curvature still be defined?
I had to add to the comments!.. I've being trying to understand this for so long. Thank you. So far I've watched this video and the topological insulator video and they're perfect.
Berry phase on its own doesn't break any symmetries; this is usually done by the properties of the underlying lattice (ferromagnetism, for example, spontaneously breaks time reversal symmetry). I'm not sure about the details of the material you mentioned, but a quick search seems to suggest that its lattice has some magnetic properties, so that might be the origin.
Hi, this video was very helpful. thank you very much. However, there are a couple of things I still cannot get a hold on. I cannot understand why you used inversion and how it solved the global study of the berry curve effect. Also, one of the reason I tried to understand Berry Curve was this sentence: "When electrons are excited into a particular valley, they can exhibit transverse motion perpendicular to their initial velocity direction, driven by the intrinsic Berry curvature of the valley.". I still don't understand how valleys or asymmetry in valleys have intrinsic berry curves.
Thanks for the detail explanation. Based on definition Berry curvature(BC) required at least two periodic directions/k-vector. Just wondering if this could explain the quantum anomalous Hall effect, as it is purely 1D. Anomalous velocity in BC picture required at least 2D.
Hi! Well, why do you say the QAHE is purely 1d? I usually think of it as a 2d effect with 1d edge states and an insulating bulk, just like the usual quantum Hall effect.
@@XenosumPhysics The carriers transport along the 1D edge and their 1D-DOS gives the quantized-conductance. Shouldn't all these relate to the 1D edge states? I am just wondering if this could be explained in the BC theorem.
@@luowatson6246 I can't think of any concrete examples where the Berry curvature was shown to be the dominant contribution to the QAHE, but in principle I don't see why not. A strong enough Berry curvature, I'd guess, can quantized the cyclotron orbits (giving rise to a QAHE) in the same way that a real magnetic field can (usual QHE). About the dimensionality, I'm not sure if you have some effective theory in mind, but the quantized conductance that the 1d states carry is sigma_xy, which can only be defined in 2d.
@@XenosumPhysics Hi, you are right about the dimensionality, what I should say should be 1-k dimension is needed for the DOS which gives rise to the quantized conductance. What confused me so far is that the Chern number is used to characterized the QAHE, which came from a close-loop integral over the Berry curvature. As I checked Qian's 1999 prb paper there are three Berry curvature terms listed with derivatives over [dk,dt],[dkx,dky],[dx,dt] , respectively. Usually the { [dkx,dky] cross (dk/dt) }gives the anomalous velocity, but this require at least 2-k dimension, which is not the case for 1D edge states. I am wondering if the other two Berry curvature terms were responsible for the non-zero Chern number in QAHE, or the original anomalous velocity terms could still be used in this scenario. I am still learning this part, thanks very much for your inputs ^_^
@@luowatson6246 As I understand it, the anomalous velocity term is exactly what gives rise to either AHE or QAHE. It should not be ignored. Pages 223-224 of the attached reference talks about it a bit www.tandfonline.com/doi/full/10.1080/00018732.2015.1068524
As a research student starting to learn topology, this video actually gave me some useful intuition that is difficult to acquire from purely equation point of view. Thanks for the great materials. Appreciate much hope to see more from you!
same happening with me, but this video gave me some basic ideas about the subject
You should be a lecturer dude. You are the only person that has managed to explain momentum space to me
a vtuber explaining high level Physics. i had only imagined it but you are actually out here doing it.
i have to say your 3D model is very well done with hand movement and everything.
I loved the videos. You have explained them so simply that, for beginners, it is an optimistic start point. But in this video, I could not help noticing the graphene structure to be written wrong.
Keep making such videos.
Wow your video is so helpful! I've been struggling to understand berry curvature for days but you managed to explain it so well. Thanks a lot!
Could you do a video on time reversal symmetry breaking and what it means? And how are states of matter classified according to the symmetry they break!
Hi, awesome video! One important case you didn't address is spin-orbit coupling which spontaneously breaks time reversal symmetry without any giant external field or twist. Sure most materials don't show high enough S-O interactions but some actually do, resulting in a "native" non-zero berry curvature
I'm beginning research on the anamolous hall effect in anti ferromagnetic materials and this helped me understand some of the context. Thanks
hmmm... can parity invariance to induce berry curvature effects be produced by stacking two graphenes, but slightly misaligned?
Great video Xeno Sensei!
Thank you!! You are so great.
i realize that this is advanced stuff and digging into the literature is probably best than to just relying one one 15 minute video, but there are things i still find difficult to grasp about Berry curvature:
1. Is Berry curvature the property of one electron in a material, or does it involve the whole bulk? is it a function of position (and time (?)), or does it have constant value throughout?
2. Being derived from schrodinger's equation, is Berry curvature a general property of solids? does every solid crystal have it, just in most of them the effects are trivial, or can it be defined only in certain classes of materials?
3. Is the finite value of Berry curvature in a material considered a thermodynamic phase? do you need to cross certain value of pressure and temperature to get this effect or is it "on" all the time?
4. From what i understand about magnetic field and circular motion, when an electron orbits around a magnetic field, aside from its position its momentum also "orbits" in the same way (the x and y components of position are sinusoidal cos() and sin(), and both are phase-shifted 90 degrees for momentum x and y components). If Berry curvature makes orbit in momentum space, does that induce circular motion in electron position also, producing a magnetic field? do magnetic field and Berry curvature couple to each other?
5. What happens if positive charge carriers (like holes) are involved? can Berry curvature still be defined?
You have an interesting research. I hope you find papers and references.
I had to add to the comments!.. I've being trying to understand this for so long. Thank you. So far I've watched this video and the topological insulator video and they're perfect.
Great explanation of the topic!
Thank you for this beautiful video.. you really made it so easy to somewhat grasp these abstract concepts.. 🔥🔥
AHE is a good way of detecting where the magnetic moment is currently pointing at, when it comes to spintronics research.
cool owo
yup
The way you explain is really awesome , could you please make a video on Landau levels by Pseudo magnetic field?
The jargon was both simple and complicated. I like this.
ʕ·ᴥ·ʔ
it likes u too
I want to ask whether the berry phase breaks the time reversal symmetry? Re cently the AHE in the AV3Sb5 sample seems to be complicated to understand.
Berry phase on its own doesn't break any symmetries; this is usually done by the properties of the underlying lattice (ferromagnetism, for example, spontaneously breaks time reversal symmetry). I'm not sure about the details of the material you mentioned, but a quick search seems to suggest that its lattice has some magnetic properties, so that might be the origin.
Hi, this video was very helpful. thank you very much. However, there are a couple of things I still cannot get a hold on.
I cannot understand why you used inversion and how it solved the global study of the berry curve effect.
Also, one of the reason I tried to understand Berry Curve was this sentence: "When electrons are excited into a particular valley, they can exhibit transverse motion perpendicular to their initial velocity direction, driven by the intrinsic Berry curvature of the valley.". I still don't understand how valleys or asymmetry in valleys have intrinsic berry curves.
another super insightful talk, tyvm!
It was so useful for me, Thanks
u r welcome c:
Thank you so much! This is very easy to understand and gives so much intuition. You help me a lot.
Thanks for the detail explanation. Based on definition Berry curvature(BC) required at least two periodic directions/k-vector. Just wondering if this could explain the quantum anomalous Hall effect, as it is purely 1D. Anomalous velocity in BC picture required at least 2D.
Hi! Well, why do you say the QAHE is purely 1d? I usually think of it as a 2d effect with 1d edge states and an insulating bulk, just like the usual quantum Hall effect.
@@XenosumPhysics The carriers transport along the 1D edge and their 1D-DOS gives the quantized-conductance. Shouldn't all these relate to the 1D edge states? I am just wondering if this could be explained in the BC theorem.
@@luowatson6246 I can't think of any concrete examples where the Berry curvature was shown to be the dominant contribution to the QAHE, but in principle I don't see why not. A strong enough Berry curvature, I'd guess, can quantized the cyclotron orbits (giving rise to a QAHE) in the same way that a real magnetic field can (usual QHE).
About the dimensionality, I'm not sure if you have some effective theory in mind, but the quantized conductance that the 1d states carry is sigma_xy, which can only be defined in 2d.
@@XenosumPhysics Hi, you are right about the dimensionality, what I should say should be 1-k dimension is needed for the DOS which gives rise to the quantized conductance.
What confused me so far is that the Chern number is used to characterized the QAHE, which came from a close-loop integral over the Berry curvature. As I checked Qian's 1999 prb paper there are three Berry curvature terms listed with derivatives over [dk,dt],[dkx,dky],[dx,dt] , respectively. Usually the { [dkx,dky] cross (dk/dt) }gives the anomalous velocity, but this require at least 2-k dimension, which is not the case for 1D edge states. I am wondering if the other two Berry curvature terms were responsible for the non-zero Chern number in QAHE, or the original anomalous velocity terms could still be used in this scenario.
I am still learning this part, thanks very much for your inputs ^_^
@@luowatson6246 As I understand it, the anomalous velocity term is exactly what gives rise to either AHE or QAHE. It should not be ignored. Pages 223-224 of the attached reference talks about it a bit
www.tandfonline.com/doi/full/10.1080/00018732.2015.1068524
I have seen blueberries in equilibrium. Or at least, they didn't move while I was looking at them. Their surfaces definitely had non-zero curvature.
Very nice video!
Wow, one can only congratulate the creator of this video clip!
Such a good explanation!
Awesome video!
great stuff, pleas make viedeos about kagome metalls.
Thanks for such a nice video
great videos! looking forward to more about condensed matter physics！
Awesome video!!! Can you please tell me, through which software are you making these animations? Thanks in advance!!
i use luppet for the avatar uwu
premiere pro for the editing
@@XenosumPhysics Thanks a lot, friend!! Have fun doing lots of research!! Enjoy!!
Condensed matter physics with a vtuber I am so in.
Any references for Anomalous Hall Effect??
References are in the description.
very nice and quite advanced..We live in that
As a graphene researcher, it's driving me nuts that you drew graphene incorrectly... Lol
1:05 lorentz field direction ,,?
Very useful, thanks!
Yess, the combination of my two favorite things. Condensed matter physics and catboys.
Wow that was awesome
not as awesome as u :D
@@XenosumPhysics This is how relationships start ;-)
Nice video, thank you Sir!
thank you for this informative video ...
Hall effect part, Lorentz force is wrong maybe
it resulted in the correct hall voltage but not because the charge carrier is positive but negative.
Very nicely explained, would love to talk to you. may I have your email? I am doing PhD in Quantum material.
Xenny best boi
:D ♥
physics uwu
Is this some new kind of hysteresis?
Thx
Bruh what does that even mean
physics is cute ok
@@SummerW2345 that sounds about right c:
i love you
🤔
Cute Xeno
Fai venire il mal di testa, basta.
It gives him a head-ache, he says.
"vtuber" Giggle
Giggle
이이게뭐노
i love u
Khetan ad
hey berry here, stop copying me
berry owo *noms*
@@XenosumPhysics u cute :3
@@w9400wg no youwu
@@w9400wg why do you sound so familiar
@@XenosumPhysics idk I don't think we ever met.
Very good video!!
great video!