New work shows that superconductivity in twisted bilayer graphene can exist away from the magic angle

New study by Caltech shows that superconductivity in twisted bilayer graphene can exist away from the magic angle when coupled to a two-dimensional semiconductor

In 2018, researchers made the surprising discovery that when you layer two sheets of single-atom-thick graphene atop one another and rotate them by precisely 1.05 degrees with respect to one another, the resulting bilayer material takes on new properties: when the density of electrons in the material is increased through the application of a voltage on a nearby electrode, it becomes a superconductor—electrons can flow freely through the material, without resistance. However, with a slight change in electron density, the bilayer becomes an insulator and prevents the flow of electrons.

Princeton team detects a cascade of electronic transitions in "magic-angle" twisted bilayer graphene

A team of researchers at Princeton has looked for the origins of the unusual behavior known as magic-angle twisted bilayer graphene, and detected signatures of a cascade of energy transitions that could help explain how superconductivity arises in this material.

"This study shows that the electrons in magic-angle graphene are in a highly correlated state even before the material becomes superconducting, "said Ali Yazdani, Professor of Physics and the leader of the team that made the discovery. "The sudden shift of energies when we add or remove an electron in this experiment provides a direct measurement of the strength of the interaction between the electrons."

MIT team finds ‘twisted’ graphene getting weirder at ‘magical angle’

Researchers at the Massachusetts Institute of Technology (MIT) have previously found a particularly strange pattern in the “twisted” graphene structure, and now they’ve studied it more closely and found that the more layers it has, the better it will work.

Graphene is a 2D carbon nanomaterial consisting of a hexagonal hexagonal grid of a hexagonal structure of carbon atoms with a sp2 hybrid orbit. This makes them functionally two-dimensional, because the electrons that move through them can only move forward/backward and sideways, not above and below. This makes graphene very conductive.

Researchers explore graphene's superconductive state

Researchers at Aalto University and the University of Jyväskylä showed that graphene can be a superconductor at a much higher temperature than expected, due to a subtle quantum mechanics effect of graphene's electrons.

The discovery of the superconducting state in twisted bilayer graphene spurred an intense debate among physicists regarding the origin of superconductivity in graphene. Although superconductivity was found only at a few degrees above the absolute zero of temperature, uncovering its origin could help understanding high-temperature superconductors and allow us to produce superconductors that operate near room temperature. Such a discovery has been considered one of the "holy grails" of physics, as it would allow operating computers with radically smaller energy consumption than today.

German researchers examine how proximity affects the resistance of graphene

A research team from the University of Göttingen, together with the Chemnitz University of Technology and the Physikalisch-Technische Bundesanstalt Braunschweig, has investigated the influence of the crystal on which graphene is grown, on the electrical resistance of the resulting material.

Contrary to previous assumptions, the new results show that the process known as the ‘proximity effect’ varies considerably at a nanometre scale. To determine the electrical resistance of graphene at the smallest scale possible, the physicists used a scanning tunneling microscope (STM).