Superconductivity: The puzzle is taking shape

Sep 13, 2011
Central part of a resistive coil at the LNCMI in Grenoble, capable of generating a continuous magnetic field of 35 Tesla. The quality of the field obtained enables NMR experiments to be conducted at frequencies of around 1.5 GHz. Credit: Bertrand Maclet / CNRS

By destabilizing superconductivity with a strong magnetic field, the electrons of a "high temperature" superconductor align into linear filaments. This phenomenon has been demonstrated by a team of researchers at the CNRS Laboratoire National des Champs Magnetiques Intenses. Published in Nature on the 8 September 2011, these results add a new piece to the puzzle that condensed-matter physicists have been trying to put together for nearly twenty-five years.

Discovered a century ago, is a spectacular phenomenon that is still intriguing researchers. What are known as "high temperature" superconductors are of particular interest to scientists, especially cuprates, i.e. copper oxides whose maximum superconducting temperature is around -140°C. How do manage to organize themselves into a single wave in these cuprates, thereby allowing the material to become a superconductor? This is the question that researchers have been trying to answer for the last twenty-five years.

It is in this context that the team from the Laboratoire National des Champs Magnétiques Intenses, in collaboration with scientists from Vancouver, subjected samples of a cuprate known as “YBaCuO” to particularly strong magnetic fields (thousands of times more powerful than those of the small magnets used on fridge doors). Using the technique of nuclear magnetic resonance, the researchers probed this superconductor at the atomic scale and discovered that electrons, under such intense fields, tend to align into rectilinear or “stripes”.

Such an alignment of charges has only ever been observed previously in non-superconducting or weakly superconducting materials but never in materials with high superconductivity. This discovery makes it possible to understand why this is so: a strong must weaken superconductivity for the effect to be observed. The results also suggest that this alignment could be an underlying tendency in all cuprates. However, it is still not clear whether this new piece of the has any relation with the superconductivity mechanism of these materials.


Explore further: Vibrational motion of a single molecule measured in real time

More information: Magnetic-field-induced charge-stripe order in the high temperature superconductor YBa2Cu3Oy l T. Wu, et al. Nature, 8 September 2011.

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rawa1
1 / 5 (1) Sep 14, 2011
IMO this effect is quite well understood already.

Inside of superconductors the electrons are repelled mutually into chaotically moving fluid. The magnetic field introduces low dimensional frustration due the Lorentz forces: the electrons repulse mutually even more, but in one directions, whereas in other direction their repulsive forces weakens. Which leads into arrangement of electrons into stripes and breaking the superconductivity.

This effect can help superconductivity instead, if the orientation of stripes would be exactly perpendicular to the direction of magnetic field lines. Which is difficult to observe inside of polycrystalline samples of cuprates, where hole stripes are oriented rather randomly. But in thin layers of superconductors the external magnetic field can really help superconductivity instead of prohibiting it. The similar effect can be observed inside of organic superconductors, which could be oriented easily.

http://atmsp.whut...7172.pdf
Macksb
1 / 5 (1) Sep 15, 2011
I also have trouble understanding the novelty in this report. Some type of internal organization is to be expected when an external, organized force of great magnitude is exerted upon (partially) mobile electrons.

I would appreciate comments from anyone who can explain why this is a surprise. The exact form of organization might be unexpected, but some order should result. Moreover, it is hard to see why this form--arising under extreme and unusual conditions--would be suprising in a cuprate superconductor, which only becomes superconducting under quite different circumstances.

I need to be pointed in the right direction to understand this report...
rawa1
1 / 5 (1) Sep 15, 2011
I need to be pointed in the right direction to understand this report...
Try to think about it from perspective of aether theory. In this model everything is composed of emergent fluctuations of hypothetical dense particle gas. What will happen if we would compress the ideal Boltzmann gas of hypothetical tiny pin-point particles? Well, these particles will arrange itself into most geometrically advantageous configuration, which is called Mott crystal. But if you increase the pressure even more, this structure will get broken and chaotic superfluous system will be formed. But if you will increase the density even more, the density fluctuations of the resulting superfluid (system of bosons) will get sufficient inertia for to behave as a new distinct colliding particles (system of fermions) and the classical gas will be formed again.
rawa1
1 / 5 (1) Sep 15, 2011
Recently physicists modelled a similar system, where the role of electrons play the excitons. Indirect excitonspairs of electrons and holes spatially separated in semiconductor bilayers or quantum wellsare known to undergo Bose-Einstein condensation and to form a quantum fluid. Authors of study show that this superfluid may crystallize upon compression. However, further compression results in quantum melting back again to a superfluid.

http://prb.aps.or.../e075130

Apparently we could find many such a similar systems. For example, recently it has been proposed, the superfluid in the core of neutron stars can condense into Mott crystal. With further increasing of pressure the asymptotic freedom of quarks applies again and the system will change into superfluid again.

http://www.techno...v/27074/

Apparently, whole Universe is arranged in such a way. The emergent zones of condensed phase are alternated with layers of superfluous vaccum etc.