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Superconductivity with transition temperature $T_c=1.7$ K has been reported in bilayer graphene [1,2]. The main factors, which may shed light on the mechanism of the formation of this superconductivity, are the following. Superconductivity…

Superconductivity · Physics 2018-06-22 G. E. Volovik

The discovery of superconductivity in twisted bilayer and twisted trilayer graphene has generated tremendous interest. The key feature of these systems is an interplay between interlayer coupling and a moir\'e superlattice that gives rise…

Stacking two layers of graphene with a relative twist angle gives rise to moir\'e patterns, which can strongly modify electronic behavior and may lead to unconventional superconductivity. A synthetic version of twisted bilayers can be…

We consider superconducting properties of a two-dimensional Dirac material such as graphene under strain that produces a flat band spectrum in the normal state. We show that in the superconducting state, such a model results in a highly…

Superconductivity · Physics 2016-06-22 V. J. Kauppila , F. Aikebaier , T. T. Heikkilä

Superconductivity is traditionally viewed as a low-temperature phenomenon. Within the BCS theory this is understood to result from the fact that the pairing of electrons takes place only close to the usually two-dimensional Fermi surface…

Materials Science · Physics 2017-11-22 Tero T. Heikkila , Grigori E. Volovik

Materials with flat electronic bands often exhibit exotic quantum phenomena owing to strong correlations. Remarkably, an isolated low-energy flat band can be induced in bilayer graphene by simply rotating the layers to 1.1$^{\circ}$,…

Mesoscale and Nanoscale Physics · Physics 2019-01-29 Matthew Yankowitz , Shaowen Chen , Hryhoriy Polshyn , K. Watanabe , T. Taniguchi , David Graf , Andrea F. Young , Cory R. Dean

The understanding of strongly-correlated materials, and in particular unconventional superconductors, has puzzled physicists for decades. Such difficulties have stimulated new research paradigms, such as ultra-cold atom lattices for…

Mesoscale and Nanoscale Physics · Physics 2018-05-22 Yuan Cao , Valla Fatemi , Shiang Fang , Kenji Watanabe , Takashi Taniguchi , Efthimios Kaxiras , Pablo Jarillo-Herrero

Several research groups have reported on the observation of superconductivity in bilayer graphene structures where single atomic layers of graphene are stacked and then twisted at angles $\theta$ forming Moir\'e superlattices. The…

Superconductivity · Physics 2020-01-15 Evgueni F. Talantsev , Ratu C. Mataira , Wayne P. Crump

Moir\'e materials have enabled the realization of flat electron bands and quantum phases that are driven by strong correlations associated with flat bands. Superconductivity has been observed, but solely, in graphene moir\'e materials. The…

Mesoscale and Nanoscale Physics · Physics 2024-05-24 Yiyu Xia , Zhongdong Han , Kenji Watanabe , Takashi Taniguchi , Jie Shan , Kin Fai Mak

Surface superconductivity in rhombohedral graphite is a robust phenomenon which can exist even when higher order hoppings between the layers lift the topological protection of the surface flat band and introduce a quadratic dispersion of…

Superconductivity · Physics 2013-05-13 N. B. Kopnin , M. Ijäs , A. Harju , T. T. Heikkilä

Recent experiments show how a bilayer graphene twisted around a certain magic angle becomes superconducting as it is doped into a region with approximate flat bands. We investigate the mean-field $s$-wave superconducting state in such a…

Superconductivity · Physics 2018-12-19 T. J. Peltonen , R. Ojajärvi , T. T. Heikkilä

Twisted bilayer graphene provides a new two-dimensional platform for studying electron interaction phenomena and flat band properties such as correlated insulator transition, superconductivity and ferromagnetism at certain magic angles.…

Mesoscale and Nanoscale Physics · Physics 2019-07-10 Liheng An , Xiangbin Cai , Meizhen Huang , Zefei Wu , Jiangxiazi Lin , Zhehan Ying , Ziqing Ye , Xuemeng Feng , Ning Wang

Superconductivity in flatband systems has attracted tremendous attention in condensed matter physics. Alternating twisted multilayer graphene presents a compelling multiband system, with a coexistence of Dirac bands and flat bands, for…

For the first time, basing both on experimental facts and our theoretical consideration, we show that Fermi systems with flat bands should be tuned with the superconducting state. Experimental measurements on magic-angle twisted bilayer…

Superconductivity · Physics 2022-05-16 V. R. Shaginyan , A. Z. Msezane , M. Ya. Amusia , G. S. Japaridze

We study the superconducting phase transition, both in a graphene bilayer and in graphite. For that purpose we derive the mean-field effective potential for a stack of graphene layers presenting hopping between adjacent sheets. For…

Superconductivity · Physics 2020-10-05 Lizardo H. C. M. Nunes , E. C. Marino , A. L. Mota

Superconductivity often occurs close to broken-symmetry parent states and is especially common in doped magnetic insulators. When twisted close to a magic relative orientation angle near 1 degree, bilayer graphene has flat moire…

We compute the phase diagram of twisted bilayer graphene near the magic angle where the occurrence of flat bands enhances the effects of electron-electron interactions and thus unleashes strongly-correlated phenomena. Most importantly, we…

Strongly Correlated Electrons · Physics 2018-12-26 Dante M. Kennes , Johannes Lischner , Christoph Karrasch

When bilayer graphene is rotationally faulted to an angle $\theta\approx 1.1^\circ$, theory predicts the formation of a flat electronic band and correlated insulating, superconducting, and ferromagnetic states have all been observed at…

Mesoscale and Nanoscale Physics · Physics 2020-09-15 Yu Saito , Jingyuan Ge , Kenji Watanabe , Takashi Taniguchi , Andrea F. Young

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…

Superconductivity · Physics 2019-09-06 Tero T. Heikkila , Timo Hyart

Flat bands may offer a route to high critical temperatures of superconductivity. It has been predicted that the quantum geometry of the bands as well as the ratio of the number of flat bands to the number of orbitals determine flat band…

Superconductivity · Physics 2025-02-04 Reko P. S. Penttilä , Kukka-Emilia Huhtinen , Päivi Törmä
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