Researchers discover first manganese based superconductor

March 19, 2015 by Bob Yirka, report

Pressure-temperature phase diagram of the helical magnet MnP [8]. Although several different magnetic phases are indicated—helical (Screw), ferromagnetic (FM), and antiferromagnetic (AFM)—all are likely to be variants of the helical phase. Suppression of the magnetism by pressure gives rise to a superconducting phase, similar to what is observed in the related helical magnet CrAs [5, 6], as seen in the inset, where the resistivity versus temperature at a pressure of 8.1 GPa is plotted. Credit: Jin-Guang Cheng/Beijing National Laboratory
(—A combined team of researchers from the Institute of Physics in China and the University of Tokyo has found the first instance of a manganese based superconductor. In their paper published in the journal Physical Review Letters, the team describes the technique they used to discover the superconductor properties in the material which many had thought would not be possible due to its high degree of magnetism.

Until recently, the idea that a material such as manganese phosphide could have a superconducting state, was ruled out because have a property where electrons formed couplets known as Cooper pairs—and magnetism disrupted them. But then it was found that using magnetism suppression techniques allowed to discover superconductor states in some organic or even iron based materials where it wasn't driven by Cooper pairs. In this new effort, the researchers worked backwards, subjecting materials to both a range of temperatures and varying degrees of pressure. That allowed them to test the properties of materials over a whole range of scenarios that might be likely to allow for a superconducting state to exist and to create phase diagrams. In so doing, they found that putting a sample of manganese phosphide in a freezer at 1K and then increasing pressure to 8 gigapascals suppressed its magnetism which led to a sudden drop in resistivity and thus a superconducting state. Also, because of the high percentage of volume fraction, the researchers were able to rule out the chance that the property was localized.

Manganese phosphide is a helical magnet, the researchers note—which suggests that other materials with a spin that is shaped like a spiral might exist. But that isn't the end of study for phosphide, thus far nothing else is known about its —that means more research will have to be done learn more about it in general and to find out if it might be useful for some applications. But meanwhile, because their technique worked so well, the researchers plan to carry out similar experiments on a wide variety of other materials to find out if some of them might have superconducting properties under certain conditions as well.

Explore further: Electron spin could be the key to high-temperature superconductivity

More information: Pressure Induced Superconductivity on the border of Magnetic Order in MnP, J.-G. Cheng, K. Matsubayashi, W. Wu, J. P. Sun, F. K. Lin, J. L. Luo, and Y. Uwatoko, Phys. Rev. Lett. 114, 117001 – Published 16 March 2015 . … ysRevLett.114.117001 . On Arxiv:

We report the discovery of superconductivity on the border of long-range magnetic order in the itinerant-electron helimagnet MnP via the application of high pressure. Superconductivity with Tsc≈1  K emerges and exists merely near the critical pressure Pc≈8  GPa, where the long-range magnetic order just vanishes. The present finding makes MnP the first Mn-based superconductor. The close proximity of superconductivity to a magnetic instability suggests an unconventional pairing mechanism. Moreover, the detailed analysis of the normal-state transport properties evidenced non-Fermi-liquid behavior and the dramatic enhancement of the quasiparticle effective mass near Pc associated with the magnetic quantum fluctuations.

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not rated yet Mar 31, 2015
All four results (helical, FM, AFM and superconducting) are consistent with a theory that I have put forth in many prior Physorg posts dating back to 2010.

My theory borrows from Art Winfree's law of coupled periodic oscillators, which he proposed circa 1967 as a mathematical proposition. He then applied it to biology. Disciples include Steve Strogatz, Bard Ermentrout, Mirollo, Kuramoto and others.

IMO Winfree's law applies to physics. See my many prior posts for specific examples. Google Macksb Winfree Physorg. Quantum = periodic oscillations.

The four results shown in the diagram are all permissible Winfree patterns. At different frequencies of oscillation (think temperature), and varying proximity of the oscillators (think pressure), different coupling patterns will be favored--these particular patterns, in fact.

At low temp and high pressure, Cooper pairs will form. Low temp means long range interactions; and high pressure forces full synchrony.
not rated yet Mar 31, 2015
Winfree's law says that systems of coupled periodic oscillators couple the cycles of their oscillations in simple ways that are the same for cycle after cycle.

A two oscillator system will couple either synchronously or anti-synchronously. For magnetism, FM is synchronous, while A (for anti) FM is exactly anti-synchronous. A general anti-synchronous model is 360 degrees in the cycle divided by X, where X is the number of oscillators. In this article, helical (screw) follows this Winfree pattern. (Helimagnetism = 360 degrees divided by say 11.). So 3 of the 4 patterns in the article clearly follow Winfree's specified patterns.

The fourth pattern is the superconductivity. IMO, the Cooper pairs arise from coupled spins (AFM pattern) plus coupled orbits (also in the anti, 180 degree apart Winfree format). Notice that the small, pink SC space is on the AFM "side" of the diagram. The very high pressure in the pink zone forces Winfree coupling of orbits too.
not rated yet Mar 31, 2015
Leaf patterns are an interesting example of Winfree's law as applied to botany. See the Wikipedia entry for phyllotaxis--the taxonomy of leaf patterns in nature. All leaf patterns follow Winfree's law. As you can see, the main leaf patterns, abstracted, are quite similar to the four patterns described in the above article.

There are many examples of Winfree patterns, such as the gaits of a horse, which follow the "allowed" Winfree patterns for a four oscillator system--the periodic oscillations of the four legs and the patterns of their coordination.

Insect legs follow Winfree patterns for a six oscillator system. Malaysian fireflies and heart cells synchronize their flashes or beats.

The only thing unusual about my theory is that no one else applies Winfree's law to physics. I do, because I believe that Max Planck's quantum of energy is a periodic oscillation. If that is correct, then Winfree's law must apply generally and extensively to physics.
1 / 5 (1) Mar 31, 2015
first manganese based superconductor
Manganese is a common component of HT superconductors - actually just this one, which Joe Eck revealed as a record Tc.

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