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One of my great surprises coming into my masters degree in condensed matter theory working with superconductors was just how poorly we understand them. We have

One of my great surprises coming into my masters degree in condensed matter theory working with superconductors was just how poorly we understand them. We have these incredibly seductive theoretical frameworks for thinking about superconductors which we know are deeply flawed, but it seems nobody (myself included) has the vision to see an alternate way of looking at them. The tyranny of the BCS theory of superconductors is real.

AnimalMuppet 7y ago
> The tyranny of the BCS theory of superconductors is real. Are you saying that the BCS theory is wrong? That it's limiting people from looking at alternate ways that could also superconduct? Or what?
- eigenspace 7y ago
  The BCS theory does a reasonably good job of describing the properties of so called ‘conventional superconductors’ which are actually a very small class, dwarfed by the ‘unconventional superconductors’ which include almost everything high-Tc. However, BCS is built upon a pile of questionable assumptions and simplifications and there are signs that it’s not even a good theory for describing conventional superconductors. I think of BCS as something of a ‘local maximum’ in the space of theories describing superconductors and we’re all stuck trying to find ways of incrementally improving the theory when really we’re going to have to make a large leap to a quite different description before real progress is made. It’s like climbing a tree to get to the moon. You get a little closer, but to get any further you’re actually going to have to climb down and do a lot of work on earth before getting any higher.
etaioinshrdlu 7y ago
Do you think it's likely that the Standard Model cannot sufficiently explain superconductivity? Or alternatively, that it can be perfectly explained, but the actual analysis is just super difficult? I find this interesting because pretty much everything else in day to day life seems to have been explained by the standard model minus gravity.
- Xcelerate 7y ago
  Like most of quantum chemistry, I imagine the Standard Model works just fine for simulating superconductivity to whatever degree of accuracy we (practically) need. The issue is finding an algorithm that can efficiently perform the calculation itself. I don't know much about condensed matter physics, but I know that for my own research in the past, something called the fermion sign problem (NP-hard) made accurate quantum chemical calculations extremely difficult.
  - acqq 7y ago
    Thanks for mentioning the term that I was able to find: https://en.wikipedia.org/wiki/Numerical_sign_problem https://en.wikipedia.org/wiki/Numerical_sign_problem https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.94.170201 https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.94... "Computational Complexity and Fundamental Limitations to Fermionic Quantum Monte Carlo Simulations, Matthias Troyer and Uwe-Jens Wiese, Phys. Rev. Lett. 94, 170201, 4 May 2005" "Quantum Monte Carlo simulations, while being efficient for bosons, suffer from the “negative sign problem” when applied to fermions — causing an exponential increase of the computing time with the number of particles. A polynomial time solution to the sign problem is highly desired since it would provide an unbiased and numerically exact method to simulate correlated quantum systems. Here we show that such a solution is almost certainly unattainable by proving that the sign problem is nondeterministic polynomial (NP) hard, implying that a generic solution of the sign problem would also solve all problems in the complexity class NP in polynomial time." https://arxiv.org/abs/cond-mat/0408370 https://arxiv.org/abs/cond-mat/0408370
    - eigenspace 7y ago
      It should be noted as well that the sign-problem shows up for many (most of the interesting ones anyway) bosonic systems as well.
    - AstralStorm 7y ago
      NP hard means that a quantum computing will not solve this problem efficiently either, as that's BQP class. (We do not know how to implement any MA or QMA efficiently.)
perlgeek 7y ago
I only heard about high temperature superconductor theory through one seminar + lab, and I too got the impression that nobody really understood this stuff -- at least not good enough to make solid predictions, and to explain it to a physics undergrad. I'm glad somebody else shares this sentiment, and it wasn't just me being dense.
scotradamus 7y ago
I wouldn't so casually dismiss BCS theory. BCS contains one of only a few exactly solvable wave functions. It's used in everything from superconductivity to neutron stars. Actually, anytime there is a fermi sea instability BCS is a good starting framework. It's an triumph of modern physics.
- eigenspace 7y ago
  There’s a reason I call the BCS theory “seductive”. It’s striking, beautiful and powerful. I also think it’s clear that BCS is far from the whole story when it comes to superconductivity and I also think the huge success of the BCS theory has cast a long shadow which makes developments in different directions more difficult.
poelzi 7y ago
With the fractional quantum hall effect, it should be clear at the latest, that neither the common electron nor the BCS superconductivity model can be true. I follow Stoyan Sargs "Basic Structures of Matter - Supergravitation Unified Theory" model, which has a very different understand of SC and solves most problems in physics. Due the fact that the electron is also quite different, the FQHE becomes easily explained. The Electron is a open, complexly formed, 3 body object with internal oscillations. In a superconductor environment, the overall structure disintegrates and build a train of electron shells and positrons. Same happens under certain effects that "create positrons". According to BSM, you can't create positrons, only shoot them out of their electron shell. Superconductivity is only a state of the vacuum in which the energy of the CL node is below a certain energy threshold, that sits between the parma and diamagnetic domains. Chapter 2, 3, 4 and 6 explain this in great detail. They are surely 200 pages together, so explaining the details enough for this to make sense is unfortunately outside the scope what a comment field can provide :) If you wonder, the reaction of electron + positron creates a compound particle of electron + positron mass but neutral charge as well as photons. It's relative stable and quite hard to detect.
- eigenspace 7y ago
  > With the fractional quantum hall effect, it should be clear at the latest, that neither the common electron nor the BCS superconductivity model can be true. I don’t think you’re interpreting the outcome of the FQHE correctly. > I follow Stoyan Sargs "Basic Structures of Matter - Supergravitation Unified Theory" model, which has a very different understand of SC and solves most problems in physics. I don’t mean to be rude here, but I went and looked up this book and found that it was full of crackpot nonsense, and nearly all the reviews on the amazon page seemed to be planted fake reviews. So I’m going to be as clear as I can here in case anyone not in the field gets curious about this POV: This is nonsense.
  - poelzi 7y ago
    I studied philosophy and physics in my youth and I can distinguish between a genius and a "crackpot" very well. Details are what counts, you can get every model to fit roughly if you don't care about the number of constants involved. If the model is correct, it also works for extreme situation. FQHE is the extrem situation that breaks the electron and SC model. I have not heard any "crackpot" to distinguish between classical logic and mathematical one, because this is something only well studied people with background in logic and philosophy of science do. This was on of the hints that made me realize this guy is good, really good. Science is always 80 years ahead of current discussion: https://www.pnas.org/content/112/24/7426 https://www.pnas.org/content/112/24/7426 We are talking about interdisciplinary physics here, it's the top rank. It took me a year to really understand Stoyans Model. Now I'm in a paradox free, consistent world view with the fewest possible assumptions you can possible make. For me galaxies and the the universe as a whole, is the logical and deterministic consequence from the lowest number of fundamental particles you can have. The world became a very complex, deterministic machine of utter beauty. I understand the fine structure constant, 137, relativity (I only can smile on your implementation of it), time, Newtonian mass, magnetic fields, planetary fields (origin), gravity, electron orbit conditions, the periodic table in it's fullest (why), quasars, pulsars, globular clusters, periodicity of the redshift, lyman alpha forest, black holes, super-massive black holes (totally different object), photons, beta-particles, ... the list goes on. I understand the internal discrepancies inside the standard model, I know for a fact, that most parts of it are in fact falsified. If you bring up a error in the math equations or a logical error in the theory of his, I would be glad to discuss this in detail. So far, I have not found a problem and in fact, came to the conclusion that this is the first model I can remotely accept as true, because it is complex and not complicated. Just some weeks ago, another confirmation from a different model with quite close values was presented at a physics conference I attended. His was ~10^27 N/m² and in BSM its 1.3 * 10^26 N/m² of Vacuum pressure, a hidden variable in the standard model.

AnimalMuppet 7y ago

> The tyranny of the BCS theory of superconductors is real. Are you saying that the BCS theory is wrong? That it's limiting people from looking at alternate ways that could also superconduct? Or what?

eigenspace 7y ago
The BCS theory does a reasonably good job of describing the properties of so called ‘conventional superconductors’ which are actually a very small class, dwarfed by the ‘unconventional superconductors’ which include almost everything high-Tc. However, BCS is built upon a pile of questionable assumptions and simplifications and there are signs that it’s not even a good theory for describing conventional superconductors. I think of BCS as something of a ‘local maximum’ in the space of theories describing superconductors and we’re all stuck trying to find ways of incrementally improving the theory when really we’re going to have to make a large leap to a quite different description before real progress is made. It’s like climbing a tree to get to the moon. You get a little closer, but to get any further you’re actually going to have to climb down and do a lot of work on earth before getting any higher.

etaioinshrdlu 7y ago

Do you think it's likely that the Standard Model cannot sufficiently explain superconductivity? Or alternatively, that it can be perfectly explained, but the actual analysis is just super difficult? I find this interesting because pretty much everything else in day to day life seems to have been explained by the standard model minus gravity.

Xcelerate 7y ago
Like most of quantum chemistry, I imagine the Standard Model works just fine for simulating superconductivity to whatever degree of accuracy we (practically) need. The issue is finding an algorithm that can efficiently perform the calculation itself. I don't know much about condensed matter physics, but I know that for my own research in the past, something called the fermion sign problem (NP-hard) made accurate quantum chemical calculations extremely difficult.
- acqq 7y ago
  Thanks for mentioning the term that I was able to find: https://en.wikipedia.org/wiki/Numerical_sign_problem https://en.wikipedia.org/wiki/Numerical_sign_problem https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.94.170201 https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.94... "Computational Complexity and Fundamental Limitations to Fermionic Quantum Monte Carlo Simulations, Matthias Troyer and Uwe-Jens Wiese, Phys. Rev. Lett. 94, 170201, 4 May 2005" "Quantum Monte Carlo simulations, while being efficient for bosons, suffer from the “negative sign problem” when applied to fermions — causing an exponential increase of the computing time with the number of particles. A polynomial time solution to the sign problem is highly desired since it would provide an unbiased and numerically exact method to simulate correlated quantum systems. Here we show that such a solution is almost certainly unattainable by proving that the sign problem is nondeterministic polynomial (NP) hard, implying that a generic solution of the sign problem would also solve all problems in the complexity class NP in polynomial time." https://arxiv.org/abs/cond-mat/0408370 https://arxiv.org/abs/cond-mat/0408370
  - eigenspace 7y ago
    It should be noted as well that the sign-problem shows up for many (most of the interesting ones anyway) bosonic systems as well.
  - AstralStorm 7y ago
    NP hard means that a quantum computing will not solve this problem efficiently either, as that's BQP class. (We do not know how to implement any MA or QMA efficiently.)

perlgeek 7y ago

I only heard about high temperature superconductor theory through one seminar + lab, and I too got the impression that nobody really understood this stuff -- at least not good enough to make solid predictions, and to explain it to a physics undergrad. I'm glad somebody else shares this sentiment, and it wasn't just me being dense.

scotradamus 7y ago

I wouldn't so casually dismiss BCS theory. BCS contains one of only a few exactly solvable wave functions. It's used in everything from superconductivity to neutron stars. Actually, anytime there is a fermi sea instability BCS is a good starting framework. It's an triumph of modern physics.

eigenspace 7y ago
There’s a reason I call the BCS theory “seductive”. It’s striking, beautiful and powerful. I also think it’s clear that BCS is far from the whole story when it comes to superconductivity and I also think the huge success of the BCS theory has cast a long shadow which makes developments in different directions more difficult.

poelzi 7y ago

With the fractional quantum hall effect, it should be clear at the latest, that neither the common electron nor the BCS superconductivity model can be true. I follow Stoyan Sargs "Basic Structures of Matter - Supergravitation Unified Theory" model, which has a very different understand of SC and solves most problems in physics. Due the fact that the electron is also quite different, the FQHE becomes easily explained. The Electron is a open, complexly formed, 3 body object with internal oscillations. In a superconductor environment, the overall structure disintegrates and build a train of electron shells and positrons. Same happens under certain effects that "create positrons". According to BSM, you can't create positrons, only shoot them out of their electron shell. Superconductivity is only a state of the vacuum in which the energy of the CL node is below a certain energy threshold, that sits between the parma and diamagnetic domains. Chapter 2, 3, 4 and 6 explain this in great detail. They are surely 200 pages together, so explaining the details enough for this to make sense is unfortunately outside the scope what a comment field can provide :) If you wonder, the reaction of electron + positron creates a compound particle of electron + positron mass but neutral charge as well as photons. It's relative stable and quite hard to detect.

eigenspace 7y ago
> With the fractional quantum hall effect, it should be clear at the latest, that neither the common electron nor the BCS superconductivity model can be true. I don’t think you’re interpreting the outcome of the FQHE correctly. > I follow Stoyan Sargs "Basic Structures of Matter - Supergravitation Unified Theory" model, which has a very different understand of SC and solves most problems in physics. I don’t mean to be rude here, but I went and looked up this book and found that it was full of crackpot nonsense, and nearly all the reviews on the amazon page seemed to be planted fake reviews. So I’m going to be as clear as I can here in case anyone not in the field gets curious about this POV: This is nonsense.
- poelzi 7y ago
  I studied philosophy and physics in my youth and I can distinguish between a genius and a "crackpot" very well. Details are what counts, you can get every model to fit roughly if you don't care about the number of constants involved. If the model is correct, it also works for extreme situation. FQHE is the extrem situation that breaks the electron and SC model. I have not heard any "crackpot" to distinguish between classical logic and mathematical one, because this is something only well studied people with background in logic and philosophy of science do. This was on of the hints that made me realize this guy is good, really good. Science is always 80 years ahead of current discussion: https://www.pnas.org/content/112/24/7426 https://www.pnas.org/content/112/24/7426 We are talking about interdisciplinary physics here, it's the top rank. It took me a year to really understand Stoyans Model. Now I'm in a paradox free, consistent world view with the fewest possible assumptions you can possible make. For me galaxies and the the universe as a whole, is the logical and deterministic consequence from the lowest number of fundamental particles you can have. The world became a very complex, deterministic machine of utter beauty. I understand the fine structure constant, 137, relativity (I only can smile on your implementation of it), time, Newtonian mass, magnetic fields, planetary fields (origin), gravity, electron orbit conditions, the periodic table in it's fullest (why), quasars, pulsars, globular clusters, periodicity of the redshift, lyman alpha forest, black holes, super-massive black holes (totally different object), photons, beta-particles, ... the list goes on. I understand the internal discrepancies inside the standard model, I know for a fact, that most parts of it are in fact falsified. If you bring up a error in the math equations or a logical error in the theory of his, I would be glad to discuss this in detail. So far, I have not found a problem and in fact, came to the conclusion that this is the first model I can remotely accept as true, because it is complex and not complicated. Just some weeks ago, another confirmation from a different model with quite close values was presented at a physics conference I attended. His was ~10^27 N/m² and in BSM its 1.3 * 10^26 N/m² of Vacuum pressure, a hidden variable in the standard model.