Editing Superconductivity (section)

=== 2D materials ===
Multiple types of superconductivity are reported in devices made of [[single-layer materials]]. Some of these materials can switch between conducting, insulating, and other behaviors.<ref name=":0">{{Cite web |last=Wood |first=Charlie |date=2024-12-06 |title=Exotic New Superconductors Delight and Confound |url=https://www.quantamagazine.org/exotic-new-superconductors-delight-and-confound-20241206/ |access-date=2025-04-17 |website=Quanta Magazine |language=en}}</ref>

Twisting materials imbues them with a “[[moiré]]” pattern involving tiled hexagonal cells that act like atoms and host electrons. In this environment, the electrons move slowly enough for their collective interactions to guide their behavior. When each cell has a single electron, the electrons take on an antiferromagnetic arrangement; each electron can have a preferred location and magnetic orientation. Their intrinsic magnetic fields tend to alternate between pointing up and down. Adding electrons allows superconductivity by causing Cooper pairs to form. Fu and Schrade argued that electron-on-electron action was allowing both antiferromagnetic and superconducting states.<ref>{{Cite journal |last=Rini |first=Matteo |date=2022-03-16 |title=Explaining Superconductivity in 2D Materials |url=https://physics.aps.org/articles/v15/s36 |journal=Physics |language=en |volume=15 |pages=s36 |doi=10.1103/PhysRevB.105.094506|arxiv=2112.03950 }}</ref>

The first success with 2D materials involved a twisted bilayer graphene sheet (2018, Tc ~1.7 K, 1.1° twist). A twisted three-layer graphene device was later shown to superconduct (2021, Tc ~2.8 K). Then an untwisted trilayer graphene device was reported to superconduct (2022, Tc 1-2 K). The latter was later shown to be tunable, easily reproducing behavior found millions of other configurations. Directly observing what happens when electrons are added to a material or slightly weakening its electric field lets physicists quickly try out an unprecedented number of recipes to see which lead to superconductivity.<ref name=":0" />

These devices have applications i.n [[quantum computing]].

2D materials other than graphene have also been made to superconduct. [[Transition metal dichalcogenides|Transition metal dichalcogenide]] (TMD) sheets twisted at 5 degrees intermittently achieved superconduction. by creating a Josephson junction. The device used used thin layers of [[palladium]] to connect to the sides of a [[tungsten telluride]] layer surrounded and protected by [[boron nitride]].<ref>{{Cite web |last=RIKEN |title=A superconducting junction made from a single 2D material promises to harness strange new physics |url=https://phys.org/news/2023-12-superconducting-junction-2d-material-harness.html |access-date=2025-04-21 |website=phys.org |language=en}}</ref> Another group demonstrated superconduction in [[molybdenum telluride]] (MoTe₂) in 2D [[Van der Waals molecule|van der Waals]] materials using ferroelectric domain walls. The Tc was implied to be higher than typical TMDs (~5–10 K).<ref>{{Cite web |date=2025-01-11 |title=New Link Found Between Ferroelectric Domain Walls and Superconductivity in 2D Materials |url=https://www.gadgets360.com/science/news/new-link-between-ferroelectric-domain-walls-and-superconductivity-in-2d-materials-7441719 |access-date=2025-04-21 |website=Gadgets 360 |language=en}}</ref>

A Cornell group added a 3.5-degree twist to an insulator that allowed electrons to slow down and interact strongly, leaving one electron per cell, exhibiting superconduction. Existing theories do not explain this behavior.

Fu and collaborators proposed that electrons arranged to form a repeating crystal that allows the electron grid to float independently of the background atomic nuclei allows the electron grid to relax. Its ripples pair electrons the way phonons do, although this is unconfirmed.