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Near a magic twist angle, bilayer graphene transforms from a weakly correlated Fermi liquid to a strongly correlated two-dimensional electron system with properties that are extraordinarily sensitive to carrier density and to controllable…

Mesoscale and Nanoscale Physics · Physics 2020-12-14 Eva Y. Andrei , Allan H. MacDonald

A variational ground state for insulating bilayer graphene (BLG), subject to quantizing magnetic fields, is proposed. Due to the Zeeman coupling, the layer anti-ferromagnet (LAF) order parameter in fully gapped BLG gets projected onto the…

Mesoscale and Nanoscale Physics · Physics 2014-06-20 Bitan Roy

We re-examine the nature of the ground states of bilayer graphene at odd integer filling factors within a simplified model of nearly degenerate $n=0$ and $n=1$ Landau levels. Previous Hartree-Fock studies have found that ferroelectric…

Strongly Correlated Electrons · Physics 2019-04-03 Thierry Jolicoeur , Csaba Tőke , Inti Sodemann

The quantum Hall effect near the charge neutrality point in bilayer graphene is investigated in high magnetic fields of up to 35 T using electronic transport measurements. In the high field regime, the eight-fold degeneracy in the zero…

Mesoscale and Nanoscale Physics · Physics 2015-05-14 Y. Zhao , P. Cadden-Zimansky , Z. Jiang , P. Kim

Divergent density of states offers the unique opportunity to explore a wide variety of correlated electron physics. In the thinnest limit, this has been predicted and verified in the ultra-flat bands of magic-angle twisted bilayer graphene,…

Mesoscale and Nanoscale Physics · Physics 2022-08-15 Anna M. Seiler , Fabian R. Geisenhof , Felix Winterer , Kenji Watanabe , Takashi Taniguchi , Tianyi Xu , Fan Zhang , R. Thomas Weitz

The relativistic-like behavior of electrons in graphene significantly influences the interaction properties of these electrons in a quantizing magnetic field, resulting in more stable fractional quantum Hall effect states as compared to…

Mesoscale and Nanoscale Physics · Physics 2015-06-15 Tapash Chakraborty , Vadim Apalkov

Bilayer graphene (BLG) offers a rich platform for broken symmetry states stabilized by interactions. In this work we study the phase diagram of BLG in the quantum Hall regime at filling factor $\nu=0$ within the Hartree-Fock approximation.…

Strongly Correlated Electrons · Physics 2017-12-27 Ganpathy Murthy , Efrat Shimshoni , Herbert Fertig

We study the magnetotransport properties of dual-gated graphene bilayers, in which the total density and layer density imbalance are independently controlled. As the bilayer is imbalanced we observe the emergence of a quantum Hall state…

Mesoscale and Nanoscale Physics · Physics 2009-09-15 Seyoung Kim , E. Tutuc

Bilayer graphene has been predicted to give unprecedented tunability of the electron-electron interaction with the help of external parameters, allowing one to stabilize different fractional quantum Hall states. Recent experimental works…

Strongly Correlated Electrons · Physics 2015-05-15 Kyrylo Snizhko , Vadim Cheianov , Steven H. Simon

The rich phase diagram of quantum spin-ladder systems has attracted much attention in the theoretical literature. The progress in experimental realisations of this fascinating physics however has been much slower. While materials with a…

Mesoscale and Nanoscale Physics · Physics 2015-11-05 Victoria Mazo , Chia-Wei Huang , Efrat Shimshoni , Sam T. Carr , H. A. Fertig

We engineer a system of two strongly confined quantum dots to gain reproducible electrostatic control of the spin at zero magnetic field. Coupling the dots in a tight ring-shaped potential with two tunnel barriers, we demonstrate that an…

We present a theory of graphene quantum rings designed to produce degenerate shells of single particle states close to the Fermi level. We show that populating these shells with carriers using a gate leads to correlated ground states with…

Materials Science · Physics 2013-05-29 P. Potasz , A. D. Güçlü , P. Hawrylak

Because of its large density-of-states and the 2{\pi} Berry phase near its low-energy band-contact points, neutral bilayer graphene (BLG) at zero magnetic field (B) is susceptible to chiral-symmetry breaking, leading to a variety of gapped…

Mesoscale and Nanoscale Physics · Physics 2014-09-03 J. Velasco , Y. Lee , Fan Zhang , Kevin Myhro , David Tran , Michael Deo , Dmitry Smirnov , A. H. MacDonald , C. N. Lau

Charge-neutral conducting systems represent a class of materials with unusual properties governed by electron-hole (e-h) interactions. Depending on the quasiparticles' statistics, band structure, and device geometry these semimetallic…

Mesoscale and Nanoscale Physics · Physics 2023-03-23 D. A. Bandurin , A. Principi , I. Y. Phinney , T. Taniguchi , K. Watanabe , P. Jarillo-Herrero

In a quantizing magnetic field, the chiral two-dimensional electron gas in Landau level $N=0$ of bilayer graphene goes through a series of phase transitions at integer filling factors $\nu \in \left[ -3,3\right] $ when the strength of an…

Mesoscale and Nanoscale Physics · Physics 2015-10-28 R. Côté , Manuel Barrette , Élie Bouffard

Evidence of flat-band magnetism and half-metallicity in compressed twisted bilayer graphene is provided with first-principles calculations. We show that dynamic band-structure engineering in twisted bilayer graphene is possible by…

Materials Science · Physics 2019-06-05 Alejandro Lopez-Bezanilla

The multi-component nature of bilayer graphene (BLG), together with the ability to controllably tune between the various ground state orders, makes it a rich system in which to explore interaction driven phenomena. In the fractional quantum…

Mesoscale and Nanoscale Physics · Physics 2017-10-25 J. I. A. Li , C. Tan , S. Chen , Y. Zeng , T. Taniguchi , K. Watanabe , J. Hone , C. R. Dean

We propose a new method to use gapped graphene as barrier to confine electrons in gapless graphene and form a good quantum dot, which can be realized on an oxygen-terminated $SiO_{2}$ substrate partly H-passivated. In particular, we use…

Mesoscale and Nanoscale Physics · Physics 2009-10-27 Qiong Ma , Zhi-Rong Lin , Tao Tu , Guang-Can Guo , Guo-Ping Guo

We study the electronic properties of dual-gated electron-hole bilayers in which the two layers are separated by a perfectly opaque tunnel barrier. Combining an electrostatic and thermodynamic analysis with mean-field theory estimates of…

Mesoscale and Nanoscale Physics · Physics 2020-09-09 Yongxin Zeng , A. H. MacDonald

Twisted van der Waals heterostructures with flat electronic bands have recently emerged as a platform for realizing correlated and topological states with an extraordinary degree of control and tunability. In graphene-based moir\'e…