Superconductivity seen in a new light

March 31, 2016, University of Geneva
Artist's impression of a high critical temperature superconductor immersed in a magnetic field. The magnetic field generates whirls of current called vortices. These allow to better perceive an ordered electronic structure that coexists with the superconducting state. Credit: © UNIGE - Xavier Ravinet

Superconducting materials have the characteristic of letting an electric current flow without resistance. The study of superconductors with a high critical temperature discovered in the 1980s remains a very attractive research subject for physicists. Indeed, many experimental observations still lack an adequate theoretical description. Researchers from the University of Geneva (UNIGE) in Switzerland and the Technical University Munich in Germany have lifted the veil on the electronic characteristics of high-temperature superconductors. Their research, published in Nature Communications, shows that the electronic densities measured in these superconductors are a combination of two separate effects. As a result, they propose a new model that suggests the existence of two coexisting states rather than competing ones postulated for the past thirty years, a small revolution in the world of superconductivity.

Below a certain temperature, a superconducting material loses all electrical resistance (equal to zero). When immersed in a magnetic field, (high-Tc) allow this field to penetrate in the form of filamentary regions, called vortices, a condition in which the material is no longer superconducting. Each vortex is a whirl of electronic currents generating their own magnetic fields and in which the electronic structure is different from the rest of the material.

Coexistence rather than competition

Some theoretical models describe high-Tc superconductors as a competition between two fundamental , each developing its own spectral signature. The first is characterized by an ordered spatial arrangement of electrons. The second, corresponding to the superconducting phase, is characterized by electrons assembled in pairs.

"However, by measuring the density of electronic states with local tunneling spectroscopy, we discovered that the spectra that were attributed solely to the core of a vortex, where the material is not in the superconducting state, are also present elsewhere—that is to say, in areas where the superconducting state exists. This implies that these spectroscopic signatures do not originate in the vortex cores and cannot be in competition with the superconducting state," explains Christoph Renner, professor in the Department of Quantum Matter Physics of the Faculty of Science at UNIGE. "This study therefore questions the view that these two states are in competition, as largely assumed until now. Instead, they turn out to be two coexisting states that together contribute to the measured spectra," professor Renner says. Indeed, physicists from UNIGE using theoretical simulation tools have shown that the experimental spectra can be reproduced perfectly by considering the superposition of the spectroscopic signature of a superconductor and this other electronic signature, brought to light through this new research.

This discovery is a breakthrough toward understanding the nature of the high-temperature . It challenges some based on the competition of the two states mentioned above. It also sheds new light on the electronic nature of the vortex cores, which potentially has an impact on their dynamics. Mastery of these dynamics, and particularly of the anchoring of vortices that depend on their electronic nature, is critical for many applications such as high-field electromagnets.

Explore further: How to maximize the superconducting critical temperature in a molecular superconductor

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Hyperfuzzy
1 / 5 (2) Mar 31, 2016
Heat is well defined. It's phonon is defined as a property of the atomic structure. Interesting research, first seek an analog to a clear medium for electrons. Notice that the atom would repel any current flow. This will allow atomic motion and heat, i.e. resistance. So if the entire structure is the absorber of the Newtonian counter reaction, then no heat, i.e. superconductor. Something like freezing the entire structure. So looking for high temperature superconductor is like sorting solids, liquids, and gases. Only thing, you might have to simulate the solid, liquid, or gas you are looking. This Easter Egg hunt is tedious.
Hyperfuzzy
1 / 5 (2) Mar 31, 2016
So the trick will be current flow and only a body response which produces no heat. To see this on the atomic scale, every motion produces a field response. Your spectra tabulates this. The spectra of interest is that which causes more atomic motion. If it only causes electron motion, not so bad unless collectively it moves the atom singularly then it's neighbor, etc.. Get it. It's a balancing act. Very difficult, but doable. Note that the residue of the field response that caused the motion will be in the infrared, i.e. between atoms, molecules. It's this production in the infrared we seek to avoid. How, I dunno. But with a good model, we can calculate the causal effects. Then build a model to avoid the same. Something like that.
Hyperfuzzy
1 / 5 (2) Mar 31, 2016
Note: Not trying to define a non-response medium. There's always a response, but what we want is the response to be more current or maybe a non-heating audio, or som'n som'n. Why not?
Hyperfuzzy
1 / 5 (2) Mar 31, 2016
Note: QM is not definitive enough, you will need to successfully simulate atomic structure and the response to any field. Not sure if your e&p should be transparent objects that always exist and the fields are always present and move in sync. Let the neutron be a combo e&p and the separation cause oscillation, i.e. the neutrino. Team: Graphics, MSEE, PhD, prefer 3 each from the best. And open minded. Define the future! Please ignore Dr. E and the standard model. That's nonsense. There is no such thing as mass, only charge. Don't trust the universal constants. Begin where Maxwell left off. Follow Faraday, to bad Farady didn't have more knowledge.
compose
Mar 31, 2016
This comment has been removed by a moderator.
compose
Mar 31, 2016
This comment has been removed by a moderator.
Hyperfuzzy
1 / 5 (1) Mar 31, 2016
All matter has revolving electrons; antimatter, revolving protons. A free electron in space see's no resistance. The point, impedance by the atom or molecule produces heat. Impedance by another electron either inductive, amplification, or attenuation, or modulation of a field that moves the atom or molecule. It doesn't matter what you call it. The point is to allow the electrons to satisfy the potential applied with a current and none of the molecular or atomic motion. C'est vrai?

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