3 ms·

It's like ties in a railroad track, if you find a stride that matches an integer multiple of the tie distance you can run like it was normal ground. The natura

It's like ties in a railroad track, if you find a stride that matches an integer multiple of the tie distance you can run like it was normal ground. The natural "stride" of an electron might be more than 2.6 nanometers. It could be they swing side to side a bit if the distance isn't quite right. Some experimentation is now in order. 2.6 Nanometers is about 5 atoms of silicon between peaks. I'm trying to find out the size of the cell created between sheets of graphene at the "magic angle" of 1.56 degrees. It may be that you simply need to construct the right geometry between nodes to get superconductivity. Regardless of the underlying quantum mechanics, there's a large opening for experimental physics here. Are there edge effects, what about grain boundaries, etc.

tomxor 4y ago
That's an interesting idea, it sounds a lot like nanotechnology that exploits various quantum effects. My extremely layman understanding notices the currently known high temperature super conductors are crystalline, structure seems to matter, but whether a nanoscale structure above this could possibly have any significant effect? It would be nice to get the opinion of someone less vaguely educated on the subject :)
- z2h-a6n 4y ago
  To provide some rough intuition, I might point out that in order for a material to become superconducting, there must be some interaction in the material that allows the electrons to form Cooper pairs, and these interactions are more likely to occur in crystalline systems. In typical BCS superconductors for example, the electrons interact with atomic lattice vibrations (called phonons) to form these pairs. The work being discussed indicates that the relevant interactions are (magnetic) superexchange interactions between electrons are relevant in the cuprates (although I'd say more work is necessary to be sure). In both cases, the structure of the crystal lattice is important for determining how these interactions take place. That said, I'm aware of some amorphous (i.e. non-crystalline) superconductors, although I'm by no means an expert in these. Another point to consider is that most chemically homogeneous solids are in principle crystalline, although in practice a chunk of matieral may be made of very many tiny crystals stuck together in random orientations. As for whether nanoscale structure could have a significant effect, that question forms a pretty major part of my current research. The stuff I'm actively working on isn't ready to publish yet, but to repeat the example I mentioned elsewhere in the comments, my colleagues were able to increase the superconducting transition temperature of strontium titanate by almost a factor of 2 by plastic deformation (i.e. squeezing it until we start messing up the structure) [0][1] (full disclosure: I'm one of the authors of this paper). We think this basically occurs by modifying the nanoscale structure in a way that introduces mechanical strain in the crystal, and this strain in turn influences the electronic interactions in such a way as to locally increase the superconducting transition temperature. In a general sense, this is somewhat similar to the fact that in many cases, applying high pressure to many superconductors will increase their transition temperature. [0] https://www.nature.com/articles/s41563-021-01102-3 https://www.nature.com/articles/s41563-021-01102-3 [1] https://arxiv.org/abs/2005.00514 https://arxiv.org/abs/2005.00514 (same paper as above, but in a non-peer-reviewed and paywall-free version)
  - tomxor 4y ago
    Thank you !
  - mikewarot 4y ago
    Long ago, there was a company that claimed to have a way of growing a "bipoloron chain" that wasn't superconducting, but was 10^6 times (or more) as conductive as copper or silver. They called it an "ultraconductor"[1]. I give it 50/50 odds of being a scam. I've always wondered if there could be something to this, and now it sounds like there might be. I have no way to judge the merits of it personally, I just keep my eye out for things that indicate it might have been real. Also, there's this patent[2] from 3 years ago that might have been using strain to make a superconductor that previously wasn't. [1] http://www.superconductors.org/ultra.htm http://www.superconductors.org/ultra.htm [2] https://patents.google.com/patent/US20190058105A1/en https://patents.google.com/patent/US20190058105A1/en
upsidesinclude 4y ago
Electrons don't have legs, but the concept might. How does the electron wavelength compare to the incidence of the geometry? Gamma = h bar/ momentum Where, m = m*v In a DC circuit the momentum can be held fairly stable once in a state of superconductance, but v is increasing up to the breakover point. Which in turn is decreasing wavelength. Bit of a trouble for a static 'circuit'. None of that is quantum anything, but it gets you thinking.
- mikewarot 4y ago
  Electrons normally flow very slowly in a conductor, at about a snail's crawl. For a superconductor, I suspect this is not the case... the quantity of electrons through a channel will go up, but the velocity is probably stable.
z2h-a6n 4y ago
> It may be that you simply need to construct the right geometry between nodes to get superconductivity. I would say that the key thing is to construct the right interactions between electrons. That said, the geometry (or structure, as we would generally say in condensed matter physics) is one of the key parts of what determines the interactions in a material, so this is certainly one approach. In practice, it is difficult to tune the structure of most materials except by applying pressure, or by changing to a different (possibly related) material, so finely tuning the interactions by influincing the structure can be difficult (twisted bilayer graphene being a notable exception). > Regardless of the underlying quantum mechanics, there's a large opening for experimental physics here. Are there edge effects, what about grain boundaries, etc. I agree! Topological insulators and their surface states (which are in some sense "edge effects") is a pretty hot topic right now. Related to superconductivity, the research group I'm working in has been playing with introducing disorder to unconventional superconductors by plastically deforming them (i.e. squeezing them until we start to mess up the structure). Surprisingly, this has actually increased the superconducting transition temperature in some cases [0][1] (full disclosure: I'm one of the authors of this paper). As far as we can tell this "strain engineering" of the electronic properties of superconductors is basically a new subfield, so there's still a lot to learn. One of the difficulties is that in unconventional superconductors (which includes the high-Tc superconductors), theorists tend to prefer to work on idealized models of materials, since the calculations are difficult enough without introducing disorder, defects, etc. in addition. [0] https://www.nature.com/articles/s41563-021-01102-3 https://www.nature.com/articles/s41563-021-01102-3 [1] https://arxiv.org/abs/2005.00514 https://arxiv.org/abs/2005.00514 (same paper as above, but in a non-peer-reviewed and paywall-free version)

tomxor 4y ago

That's an interesting idea, it sounds a lot like nanotechnology that exploits various quantum effects. My extremely layman understanding notices the currently known high temperature super conductors are crystalline, structure seems to matter, but whether a nanoscale structure above this could possibly have any significant effect? It would be nice to get the opinion of someone less vaguely educated on the subject :)

z2h-a6n 4y ago
To provide some rough intuition, I might point out that in order for a material to become superconducting, there must be some interaction in the material that allows the electrons to form Cooper pairs, and these interactions are more likely to occur in crystalline systems. In typical BCS superconductors for example, the electrons interact with atomic lattice vibrations (called phonons) to form these pairs. The work being discussed indicates that the relevant interactions are (magnetic) superexchange interactions between electrons are relevant in the cuprates (although I'd say more work is necessary to be sure). In both cases, the structure of the crystal lattice is important for determining how these interactions take place. That said, I'm aware of some amorphous (i.e. non-crystalline) superconductors, although I'm by no means an expert in these. Another point to consider is that most chemically homogeneous solids are in principle crystalline, although in practice a chunk of matieral may be made of very many tiny crystals stuck together in random orientations. As for whether nanoscale structure could have a significant effect, that question forms a pretty major part of my current research. The stuff I'm actively working on isn't ready to publish yet, but to repeat the example I mentioned elsewhere in the comments, my colleagues were able to increase the superconducting transition temperature of strontium titanate by almost a factor of 2 by plastic deformation (i.e. squeezing it until we start messing up the structure) [0][1] (full disclosure: I'm one of the authors of this paper). We think this basically occurs by modifying the nanoscale structure in a way that introduces mechanical strain in the crystal, and this strain in turn influences the electronic interactions in such a way as to locally increase the superconducting transition temperature. In a general sense, this is somewhat similar to the fact that in many cases, applying high pressure to many superconductors will increase their transition temperature. [0] https://www.nature.com/articles/s41563-021-01102-3 https://www.nature.com/articles/s41563-021-01102-3 [1] https://arxiv.org/abs/2005.00514 https://arxiv.org/abs/2005.00514 (same paper as above, but in a non-peer-reviewed and paywall-free version)
- tomxor 4y ago
  Thank you !
- mikewarot 4y ago
  Long ago, there was a company that claimed to have a way of growing a "bipoloron chain" that wasn't superconducting, but was 10^6 times (or more) as conductive as copper or silver. They called it an "ultraconductor"[1]. I give it 50/50 odds of being a scam. I've always wondered if there could be something to this, and now it sounds like there might be. I have no way to judge the merits of it personally, I just keep my eye out for things that indicate it might have been real. Also, there's this patent[2] from 3 years ago that might have been using strain to make a superconductor that previously wasn't. [1] http://www.superconductors.org/ultra.htm http://www.superconductors.org/ultra.htm [2] https://patents.google.com/patent/US20190058105A1/en https://patents.google.com/patent/US20190058105A1/en

upsidesinclude 4y ago

Electrons don't have legs, but the concept might. How does the electron wavelength compare to the incidence of the geometry? Gamma = h bar/ momentum Where, m = m*v In a DC circuit the momentum can be held fairly stable once in a state of superconductance, but v is increasing up to the breakover point. Which in turn is decreasing wavelength. Bit of a trouble for a static 'circuit'. None of that is quantum anything, but it gets you thinking.

mikewarot 4y ago
Electrons normally flow very slowly in a conductor, at about a snail's crawl. For a superconductor, I suspect this is not the case... the quantity of electrons through a channel will go up, but the velocity is probably stable.

z2h-a6n 4y ago

> It may be that you simply need to construct the right geometry between nodes to get superconductivity. I would say that the key thing is to construct the right interactions between electrons. That said, the geometry (or structure, as we would generally say in condensed matter physics) is one of the key parts of what determines the interactions in a material, so this is certainly one approach. In practice, it is difficult to tune the structure of most materials except by applying pressure, or by changing to a different (possibly related) material, so finely tuning the interactions by influincing the structure can be difficult (twisted bilayer graphene being a notable exception). > Regardless of the underlying quantum mechanics, there's a large opening for experimental physics here. Are there edge effects, what about grain boundaries, etc. I agree! Topological insulators and their surface states (which are in some sense "edge effects") is a pretty hot topic right now. Related to superconductivity, the research group I'm working in has been playing with introducing disorder to unconventional superconductors by plastically deforming them (i.e. squeezing them until we start to mess up the structure). Surprisingly, this has actually increased the superconducting transition temperature in some cases [0][1] (full disclosure: I'm one of the authors of this paper). As far as we can tell this "strain engineering" of the electronic properties of superconductors is basically a new subfield, so there's still a lot to learn. One of the difficulties is that in unconventional superconductors (which includes the high-Tc superconductors), theorists tend to prefer to work on idealized models of materials, since the calculations are difficult enough without introducing disorder, defects, etc. in addition. [0] https://www.nature.com/articles/s41563-021-01102-3 https://www.nature.com/articles/s41563-021-01102-3 [1] https://arxiv.org/abs/2005.00514 https://arxiv.org/abs/2005.00514 (same paper as above, but in a non-peer-reviewed and paywall-free version)