Superconductor, Insulator… the graphene’s suprises

Since the discovery of graphene in 2004, scientists have found that this honeycomb-like sheet of carbon atoms is not just the thinnest material known in the world, but also incredibly light and flexible, hundreds of times stronger than steel, and more electrically conductive than copper.

It turned out recently that a sandwich of two graphene layers can be tuned, by twisting the angle between two sheets, to behave at two electrical extremes: as an insulator, in which electrons are completely blocked from flowing; and as a superconductor, in which electrical current can stream through without resistance.  More about it, here!

graphenelattice

The effects of rotation in twisted bilayer graphene. a, When a graphene bilayer is twisted so that the top sheet is rotated out of alignment with the lower sheet, the unit cell (the smallest repeating unit of the material’s 2D lattice) becomes enlarged. For large rotations, the electronic band structures of the two graphene sheets are also rotated out of alignment (not shown). b, For small rotation angles, a ‘moiré’ pattern is produced in which the local stacking arrangement varies periodically. Cao et al.1,2 have observed that, for rotation angles of less than 1.05°, regions in which the atoms are directly above each other (the lighter regions in the pattern) form narrow electron energy bands, in which electron ‘correlation’ effects are enhanced. This results in the generation of a non-conducting state2 (a Mott insulator), which can be converted into a superconducting state1 if charge carriers are added to the graphene system. [Nature, News and Views, E.J.Mele, 05 MARCH 2018]

  1. Cao, Y. et al. Nature http://dx.doi.org/10.1038/nature26160 (2018).
  2. Cao, Y. et al. Nature http://dx.doi.org/10.1038/nature26154 (2018).
Advertisements

The Nobel Prize in Physics 2016

“This year’s Laureates opened the door on an unknown world where matter exists in strange states. The Nobel Prize in Physics 2016 is awarded with one half to David J. Thouless, University of Washington, Seattle, and the other half to F. Duncan M. Haldane, Princeton University, and J. Michael Kosterlitz, Brown University, Providence. Their discoveries have brought about breakthroughs in the theoretical understanding of matter’s mysteries and created new perspectives on the development of innovative materials.

The three Laureates’ use of topological concepts in physics was decisive for their discoveries. Topology is a branch of mathematics that describes properties that only change step-wise. Using topology as a tool, they were able to astound the experts. ”

 

phasetransition

Read more about this year’s prize

Popular Science Background
Scientific Background

from  www.nobelprize.org/nobel_prizes/physics

Happy Birthday to superconductivity!

Well, it seems Google doesn’t care about the 104th Anniversary of the discovery of Superconductuvity. No #levitatingdoodle for us. Nonetheless today we celebrate superconductivity!
A nice occasion of outreach about this fascinating topic:
What is a superconductor?

#LevitatingDoodle

Superconductivity was discovered on April 8, 1911. We have launched the campaign ‪#‎LevitatingDoodle‬ to ask Google for a doodle to celebrate the anniversary of the discovery.
Come on, help us -> http://www3.icmm.csic.es/superconductividad/quienes-somos/actividades/levitating-doodle/

La superconduttività è stata scoperta l`8 Aprile del 1911. Abbiamo lanciato la campagna #LevitatingDoodle per chiedere a Google di commemorare l’ anniversario della scoperta con un doodle.
Partecipa anche tu! Scopri come qui -> http://www3.icmm.csic.es/superconductividad/quienes-somos/actividades/levitating-doodle/

On Air: Los superconductores del ICMM se hacen famosos!

Well,
it seems that our open days about superconductivity are so funny that even the spanish tv starts to be interested in condensed matter! The last episode of the Órbita Laika show (on air every sunday nigth) was dedicated to superconductivity. The experiments performed in the studios have been realized in cooperation with our team of researchers of the ICMM-CSIC.
Enjoy the video  ‘Órbita Laika – Superconductores’

La demostración de Antonio Martínez Ron en el programa número 9 de Órbita Laika (emitido en La 2 de TVE 08/02/2015) contó con la aparición estelar de nuestros superconductores y la primicia de nuestro nuevo tren!¿No lo has visto aún? No te lo pierdas!  ‘Órbita Laika – Superconductores’

For more information about the outreach activity on superconductivity of the ICMM-CSIC
take a look here

Más información sobre actividades de divulgación de superconductividad aquí