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Researchers observe double symmetrical superconductivity in 2D niobium.

Researchers observed double symmetrical superconductivity in 2D NbSe2.

Scientists have detected through electron transport and tunnel measurement. (Gray Contact) The state of a mixed plain / informal superconductor in a few atom-thick NbSe2 plates. (Blue and Yellow Circles) NbSe2 is a two-dimensional material that has received great interest in exploring new superconducting states due to the strong spinning orbital coupling from the heavily altered metal atoms. By applying a magnetic field in planes (red arrow) up to 35T at various angles θ, a double symmetrical signal (purple ellipse) is found in resistance and tunnel conductivity is found in the superconducting regime. The observed symmetry, which occurs even without a double structure in the material, demonstrates the insignificant interaction leading to the measured signal. This observation was the result of the mixing of conventional isotropic (s-wave, blue circle) superconducting spaces with anisotropic superconducting spaces (p- or d-wave, colored lobes). Dang) .This unexpected finding paved the way for further investigation of how this double behavior might occur, as well as inform future studies of mixed and informal superconductivity in biomaterials. Dimension credit: Hamill et al.

In recent years, many material scientists around the world have been investigating the potential of two-dimensional (2D) materials consisting of single-layer or ultra-thin layers of atoms and with unique physical, electrical and optical properties.

Researchers from the University of Minnesota and Cornell University recently conducted a few layers of niobium superconductivity (NbSe).2), A multilayer transition metal showing a unique ising type spin-sine orbital joint. Their paper published in Natural physicsShowed a few layers of NbSe’s superconducting state.2 It has double symmetry, which is significantly different from the crystal structure.

“There is a strong interest in two-dimensional materials such as NbSe.2Because when prepared to be only a few atomic layers, new properties often do not exist in thick samples of the same material, ”said Vlad S. Pribiag, one of the researchers in the study, Phys.org.2 Is a superconductor in bulk form. But when a few layers of sample are prepared, the crystal symmetry is changed, making the superconductivity more flexible with the applied magnetic field. This was discovered by some co-authors a few years ago and is one of the driving forces of our work. ”

Ago, researchers speculated that NbSe2 May be superconductor topology Superconductivity topology is a class of specific superconductors with insignificant properties. These characteristic superconductors are attracting great attention as they may prevent the quantum bits from losing stored information. Thus, it could enable the creation of a new, woven-protected quantum computer.

Pribiag and his colleagues’ recent work was inspired by previous studies exploring possibilities at NbSe.2 Is a superconductor topology. In their experiment, the researchers specifically examined the superconductivity of NbSe’s topology.2 That is only a few atomic layers

“We found the superconducting state of a few NbSe layers.2 It has double symmetry, which is distinctly different from the triple symmetry of the crystal. (In other words, the crystals look the same if they are rotated 120 degrees, but the superconducting state properties repeat when rotated 180 degrees), explains Pribiag. “This double symmetry corresponds to the two competing superconducting states with near energy. Very similar: One of them may be related to superconductivity, topology – and we are now running a follow-up experiment aimed at investigating this. “

In their experiments, Pribiag and colleagues found that anisotropy (ie, a property that allows materials to change physical characteristics when measured along the crystal axis in different directions) appeared as they rotated magnetic fields on the sample plane. The researchers further examined this observation using two different types of samples.

In one type of example, they measure the critical field. The second type, studied by the Cornell University team, has a thin insulating layer between NbSe.2 And magnetic materials which allow them to penetrate into NbSe.2The two measurements they gathered both showed double the anisotropy.

“Atoms in NbSe2 They are aligned in a periodic triangular form, so internal physics properties are expected to show three times the rotational equation. (Ie, rotating the system or surrounding environment by 120 degrees should result in indistinguishable physical properties before rotation), “Ke Wang, another researcher involved in the study told Phys.org. Notice the double spin symmetry of the superconducting state in a few layers of NbSe.2 Under an external magnetic field in the plane opposite threefold symmetry of the lattice “

According to the famous Bardeen-Cooper-Schrieffer (BCS) theory, which explains superconductivity, two electrons can be paired to form a bosonic pair. These pairs then lead to the formation of sparse superfluid electrons, which leads to superconductivity.

In a thick three-dimensional (3D) layer NbSe2The pairing mechanism as stated in BCS theory shows the original instability of the s wave. On the other hand, when NbSe2 Approaching the 2D limit, an unusual pairing mechanism involving d- or p-wave electrons can occur in the presence of strong orbital coupling.

“In our few examples linking 2D and 3D boundaries, the two pairing instabilities of the above mix and compete and lead to the double asymmetric superconductivity that we observe,” Wang said. explain

Pribiag, Wang, and colleagues were the first to gather clear evidence of the extraordinary pairing mechanism that occurs in 2D NbSe.2 With a few layers of atoms In addition to expanding the current understanding of 2D NbSe2 And its properties, the findings they compiled raise fundamental questions about the origin of the unusual match interactions they observed.

“Our future research will focus on answering many fundamental questions about novel pairing mechanisms leading to our latest findings,” Wang said. Does spontaneous superconductivity or intense gap blends produced by small symmetrical destructive fields, such as topological superconducting conductivity stress, play a role, as determined by our theoretical collaborators? Examine samples with different atomic thicknesses and stresses that will allow us to control the competition between the sequence parameters. ”

True 2D Superconductor NbSe2

More information:
Double symmetrical superconductors in a few layers of NbSe2. Natural physics(2021). DOI: 10.1038 / s41567-021-01219-x.

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Reference: Researchers observe double symmetrical superconductivity in 2D niobium (2021, May 12) .Retrieved May 13, 2021 from https://phys.org/news/2021-05-two-fold-symmetric-superconductivity- 2d-niobium.html

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