Thursday, August 13, 2015

Flux tube description seems to apply also to low Tc superconductivity



Discussions with Hans Geesink have inspired sharpening of the TGD view about bio-superconductivity (bio-SC), high Tc superconductivity (SC) and relate the picture to standard descriptions in a more detailed manner. In fact, also standard low temperature super-conductivity modelled using BCS theory could be based on the same universal mechanism involving pairs of magnetic flux tubes possibly forming flattened square like closed flux tubes and members of Cooper pairs residing at them.

A brief summary about strengths and weakness of BCS theory

First I try to summarise what patent reminds about BCS theory.

  1. BCS theory is successful in 3-D superconductors and explains a lot: supracurrent, diamagnetism, and thermodynamics of the superconducting state, and it has correlated many experimental data in terms of a few basic parameters.

  2. BCS theory has also failures.

    1. The dependence on crystal structure and chemistry is not well-understood: it is not possible to predict, which materials are super-conducting and which are not.

    2. High-Tc SC is not understood. Antiferromagnetism is known to be important. The quite recent experiment demonstrates conductivity- maybe even conductivity - in topological insulator in presence of magnetic field (see
      this). This is compete paradox and suggests in TGD framework that the flux tubes of external magnetic field serve as the wires (see previous posting).

  3. BCS model based on crystalline long range order and k-space (Fermi sphere). BCS-difficult materials have short range structural order: amorphous alloys, SC metal particles 0-down to 50 Angstroms (lipid layer of cell membrane) transition metals, alloys, compounds. Real space description rather than k-space description based on crystalline order seems to be more natural. Could it be that the description of electrons of Cooper pair is not correct? If so, k-space and Fermi sphere would be only appropriate description of ordinary electrons needed to model the transition to to super-conductivity? Super-conducting electrons could require different description.

  4. Local chemical bonding/real molecular description has been proposed. This is of course very natural in standard physics framework since the standard view about magnetic fields does not provide any ideas about Cooper pairing and magnetic fields are only a nuisance rather than something making SC possible. In TGD framework the situation is different.

TGD based view about SC

TGD proposal for high Tc SC and bio-SC relies on many-sheeted space-time and TGD based view about dark matter as heff=n× h phase of ordinary matter emerging at quantum criticality (see this).

Pairs of dark magnetic flux tubes would be the wires carrying dark Cooper pairs with members of the pair at the tubes of the pair. If the members of flux tube pair carry opposite B:s, Cooper pairs have spin 0. The magnetic interaction energy with the flux tube is what determines the critical temperature. High Tc superconductivity, in particular the presence of two critical temperatures can be understood. The role of anti-ferromagnetism can be understood.

TGD model is clearly x-space model: dark flux tubes are the x-space concept. Momentum space and the notion of Fermi sphere are certainly useful in understanding the transformation ordinary lattice electrons to dark electrons at flux tubes but the super conducting electron pairs at flux tubes would have different description.

Now come the heretic questions.

  1. Do the crystal structure and chemistry define the (only) fundamental parameters in SC? Could the notion of magnetic body - which of course can correlate with crystal structure and chemistry - equally important or even more important notion?

  2. Could also ordinary BCS SC be based on magnetic flux tubes? Is the value of heff=n× h only considerably smaller so that low temperatures are required since energy scale is cyclotron energy scale given by E= heff=n× fc, fc = eB/me. High Tc SC would only have larger heff and bio-superconductivity even larger heff!

  3. Could it be that also in low Tc SC there are dark flux tube pairs carrying dark magnetic fields in opposite directions and Cooper pairs flow along these pairs? The pairs could actually form closed loops: kind of flattened O:s or flattened squares.

One must be able to understand Meissner effect. Why dark SC would prevent the penetration of the ordinary magnetic field inside superconductor?
  1. Could Bext actually penetrate SC at its own space-time sheet. Could opposite field Bind at its own space-time sheet effectively interfere it to zero? In TGD this would mean generation of space-time sheet with Bind=-Bext so that test particle experiences vanishing B. This is obviously new. Fields do not superpose: only the effects caused by them superpose.

    Could dark or ordinary flux tube pairs carrying Bind be created such that the first flux tube portion Bind in the interior cancels the effect of Bext on charge carriers. The return flux of the closed flux tube of Bind would run outside SC and amplify the detected field Bext outside SC. Just as observed.

  2. What happens, when Bext penetrates to SC? heff→ h must take place for dark flux tubes whose cross-sectional area and perhaps also length scale down by heff and field strength increases by heff. If also the flux tubes of Bind are dark they would reduce in size in the transition heff→ h by 1/heff factor and would remain inside SC! Bext would not be screened anymore inside superconductor and amplified outside it! The critical value of Bext would mean criticality for this heff → h phase transition.

  3. Why and how the phase transition destroying SC takes place? Is it energetically impossible to build too strong Bind? So that effective field Beff=Bdark+ Bind+Bext experienced by electrons is reduced so that also the binding energy of Cooper pair is reduced and it becomes thermally unstable. This in turn would mean that Cooper pairs generating the dark Bdark disappear and also Bdark disappears. SC disappears.

Addition:The newest news is that hydrogen sulfide - the compound responsible for the smell of rotten eggs - conducts electricity with zero resistance at a record high temperature of 203 Kelvin (–70 degrees C), reports a paper published in Nature. This super-conductor however suffers from a serious existential crisis: it behaves very much like old fashioned super-conductor for which superconductivity is believed to be caused by lattice vibrations and is therefore not allowed to exist in the world of standard physics! To be or not to be!

TGD Universe allows however all flowers to bloom: the interpretation is that the mechanism is large enough value of heff=n×h implying that critical temperature scales up. Perhaps it is not a total accident that hydrogen sulfide H2S - chemically analogous to water - results from the bacterial breakdown of organic matter, which according to TGD is high temperature super-conductor at room temperature and mostly water, which is absolutely essential for the properties of living matter in TGD Universe.

See the chapter Quantum model for bio-superconductivity: II

For a summary of earlier postings see Links to the latest progress in TGD.

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