scholarly journals Coulomb interaction, phonons, and superconductivity in twisted bilayer graphene

2021 ◽  
Vol 118 (32) ◽  
pp. e2107874118
Author(s):  
Tommaso Cea ◽  
Francisco Guinea
Keyword(s):  
Fermi Surface ◽  
Coulomb Interaction ◽  
Crucial Role ◽  
Bilayer Graphene ◽  
Combined Effect ◽  
Large Momentum ◽  
Superconducting Gap ◽  
Cooper Pairs ◽  
Electron Hole ◽  
Twisted Bilayer Graphene

The polarizability of twisted bilayer graphene, due to the combined effect of electron–hole pairs, plasmons, and acoustic phonons, is analyzed. The screened Coulomb interaction allows for the formation of Cooper pairs and superconductivity in a significant range of twist angles and fillings. The tendency toward superconductivity is enhanced by the coupling between longitudinal phonons and electron–hole pairs. Scattering processes involving large momentum transfers, Umklapp processes, play a crucial role in the formation of Cooper pairs. The magnitude of the superconducting gap changes among the different pockets of the Fermi surface.

scholarly journals Moiré with flat bands is different

2019 ◽  
Vol 50 (3) ◽  
pp. 24-26
Author(s):  
Tero T. Heikkilä ◽  
Timo Hyart
Keyword(s):  
Critical Temperature ◽  
Fermi Surface ◽  
Room Temperature ◽  
Electronic States ◽  
Bilayer Graphene ◽  
Flat Bands ◽  
Twisted Bilayer Graphene

Recent experimental discoveries of superconductivity and other exotic electronic states in twisted bilayer graphene (TBG) call for a reconsideration of our traditional theories of these states, usually based on the assumption of the presence of a Fermi surface. Here we show how such developments may even help us finding mechanisms of increasing the critical temperature of superconductivity towards the room temperature.

scholarly journals Elastocapillary cleaning of twisted bilayer graphene interfaces

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yuan Hou ◽  
Zhaohe Dai ◽  
Shuai Zhang ◽  
Shizhe Feng ◽  
Guorui Wang ◽  
...  
Keyword(s):  
Crucial Role ◽  
Ostwald Ripening ◽  
Van Der Waals ◽  
Mechanical Stretch ◽  
Underlying Mechanism ◽  
Capillary Forces ◽  
Bilayer Graphene ◽  
Self Renewal ◽  
Ripening Process ◽  
Twisted Bilayer Graphene

AbstractAlthough layered van der Waals (vdW) materials involve vast interface areas that are often subject to contamination, vdW interactions between layers may squeeze interfacial contaminants into nanopockets. More intriguingly, those nanopockets could spontaneously coalesce into larger ones, which are easier to be squeezed out the atomic channels. Such unusual phenomena have been thought of as an Ostwald ripening process that is driven by the capillarity of the confined liquid. The underlying mechanism, however, is unclear as the crucial role played by the sheet’s elasticity has not been previously appreciated. Here, we demonstrate the coalescence of separated nanopockets and propose a cleaning mechanism in which both elastic and capillary forces are at play. We elucidate this mechanism in terms of control of the nanopocket morphology and the coalescence of nanopockets via a mechanical stretch. Besides, we demonstrate that bilayer graphene interfaces excel in self-renewal phenomena.

scholarly journals Tunneling and fluctuating electron-hole Cooper pairs in double bilayer graphene

2020 ◽  
Vol 101 (3) ◽  
Author(s):  
Dmitry K. Efimkin ◽  
G. William Burg ◽  
Emanuel Tutuc ◽  
Allan H. MacDonald
Keyword(s):  
Bilayer Graphene ◽  
Cooper Pairs ◽  
Electron Hole ◽  
Hole Cooper Pairs

Gating Electron–Hole Asymmetry in Twisted Bilayer Graphene

ACS Nano ◽  
2014 ◽  
Vol 8 (7) ◽  
pp. 6962-6969 ◽  
Author(s):  
Chao-Hui Yeh ◽  
Yung-Chang Lin ◽  
Yu-Chen Chen ◽  
Chun-Chieh Lu ◽  
Zheng Liu ◽  
...  
Keyword(s):  
Bilayer Graphene ◽  
Electron Hole ◽  
Twisted Bilayer Graphene

scholarly journals Tuning electron correlation in magic-angle twisted bilayer graphene using Coulomb screening

Science ◽  
2021 ◽  
Vol 371 (6535) ◽  
pp. 1261-1265
Author(s):  
Xiaoxue Liu ◽  
Zhi Wang ◽  
K. Watanabe ◽  
T. Taniguchi ◽  
Oskar Vafek ◽  
...  
Keyword(s):  
Coulomb Interaction ◽  
Theoretical Models ◽  
Bilayer Graphene ◽  
Magic Angle ◽  
Thick Barrier ◽  
Close Proximity ◽  
Twisted Bilayer Graphene ◽  
Quantum Phenomena ◽  
The Stability ◽  
Correlated Fermions

Controlling the strength of interactions is essential for studying quantum phenomena emerging in systems of correlated fermions. We introduce a device geometry whereby magic-angle twisted bilayer graphene is placed in close proximity to a Bernal bilayer graphene, separated by a 3-nanometer-thick barrier. By using charge screening from the Bernal bilayer, the strength of electron-electron Coulomb interaction within the twisted bilayer can be continuously tuned. Transport measurements show that tuning Coulomb screening has opposite effects on the insulating and superconducting states: As Coulomb interaction is weakened by screening, the insulating states become less robust, whereas the stability of superconductivity at the optimal doping is enhanced. The results provide important constraints on theoretical models for understanding the mechanism of superconductivity in magic-angle twisted bilayer graphene.

Sign in / Sign up

Export Citation Format

Share Document