📰 A new iron key for high-temperature superconductivity

Irig researchers are carrying out neutron scattering studies on iron-nickel-arsenic pnictide, a superconducting material at temperatures lower than those typically encountered. They succeeded in probing this compound at the atomic scale and their results could favor the proposal of a mechanism common to all materials (A material is a material of natural or artificial origin that man shapes to…) superconductors.

In a conventional superconductor, as in some metals, current flows without resistance at very low temperature (Temperature is a physical quantity measured using a thermometer and…) (

In the 1990s, new higher temperature superconducting materials (up to 135 K) were discovered. In these compounds, it is assumed that the Cooper pairs are formed thanks to the magnetism (Magnetism is a physical phenomenon, through which forces manifest…). However the exact mechanism is not yet understood. Recently, compounds based on iron-nickel-arsenic, superconducting around 50 K, have opened up prospects for understanding this mechanism. However, fundamental studies of these materials are complicated because few probes can see the current-carrying electrons interacting with the magnetic moments from atoms (An atom (from the Greek ατομος, atomos, « that one cannot…).

It is in this context (The context of an event includes the circumstances and conditions surrounding it; the…) that researchers from Irig [collaboration] carry out experiments on pnicture of iron-nickel-arsenic in order to study the dynamic (The word dynamic is often used to designate or qualify what relates to movement. It…) spins of the electrons responsible for the effect of superconductivity (Superconductivity (or superconductivity) is a phenomenon characterized by…). They thus selected CaK(Fe_1-xNeither_x)₄ace₄a new material (A material is a material of natural or artificial origin that man shapes…) composed of a layer of iron-nickel arsenide which alternately separates a layer of calcium (Calcium is a chemical element, symbol Ca and atomic number 20.) and a layer of potassium (Potassium is a chemical element, symbol K (Latin: kalium, from…). The structure of this compound is particularly interesting because the atoms of iron (Iron is a chemical element, symbol Fe and atomic number 26. It is…) form square patterns, with the magnetic moments of the iron atoms pointing to their centers (figure). This arrangement (The notion of arrangement is used in probabilities, and in particular for…) magnetic moments of iron cheek (The cheek is the part of the face that covers the oral cavity, closed by the…) an essential role in the superconducting effect.

Thanks to flow (The word flux (from the Latin fluxus, flow) generally designates a set of elements…) of neutrons generated by the Very Large Instrument of theLaue Langevin Institute (The Laue-Langevin Institute (ILL), named in honor of the physicists Max von Laue (physicist…)in Grenoble, and the instruments that Irig operates in this environment (The environment is everything that surrounds us. It is all the natural elements and…), these researchers managed to probe the compound at the atomic scale. They were thus able to highlight the origin of the coupling of the spins of the electrons with the magnetic moments of the iron atoms: the coupling causes a hustle (Stirring is the operation which consists of mixing one or more phases…) spins that come into play pair (We say that a set E is a pair when it is formed of two distinct elements…) to form the superconducting state and which are preferentially oriented along a direction perpendicular (In plane geometry, two lines are said to be perpendicular when they intersect at…) to iron-nickel-arsenic layers.

These new experiments confirm the theories for interpreting the phenomenon of superconductivity: when the material cools down to the critical temperature (for which the material becomes superconducting), the agitations of the spins incite the itinerant electrons to pair up, which favors the establishment of superconductivity. These results could favor the proposal of a mechanism common to all superconducting materials.

Diagram of the iron-nickel-arsenic compound.
the network (A computer network is a set of equipment linked together to exchange information…) square (A square is a regular polygon with four sides. This means that its…) iron atoms (blue balls) and their magnetic moments (red arrows) form horizontal layers. Perpendicularly, the electron spin agitations (e^–) accentuate their formation in pairs to favor the superconducting state at higher temperature.
Credit: Huiqian Luo team/Institute of Physics, Chinese Academy of Sciences.

Notes:

Pnictide: chemical compound formed with an element of the pnictogen family, i.e. the atoms of the fifteenth column of the board (Table can have several meanings depending on the context used:) of Mendeleïev (nitrogen N, phosphorus (Phosphorus is a chemical element of the family of pnictogens, symbol P and…) P, arsenic (Arsenic is a chemical element of the family of pnictogens, symbol…) As, antimony (Antimony is a chemical element of the family of pnictogens, symbol Sb…) sb, bismuth (Bismuth is a chemical element of the family of pnictogens, symbol Bi and…) Bi).
magnetic moment, spin (Spin is an intrinsic quantum property associated with every…): degree (The word degree has several meanings, it is notably used in fields…) internal (In France, this name designates a doctor, a pharmacist or a dental surgeon, at the…) freedom of electrons and atoms which is at the origin of magnetism in particular. They are visualized by arrows.

Collaboration:
Chinese Academy of Sciences, Laboratory Leon Brillouin (Léon Brillouin (born August 7, 1889 in Sèvres – died in 1969 in New York) was a physicist…).

References:
Liu C, Bourges P, Sidis Y, Xie T, He G, Bourdarot F, Danilkin S, Ghosh H, Ghosh S, Ma X, Li S, Li Y and Luo H
Preferred spin excitations in the bilayer iron-based superconductor CaK(Fe_0.96Neither_0.04)₄ace₄ with spin-vortex crystal order.
Physical Review Letters2022.