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SCZ Memorial Workshop
Magic Angle TBG: FQHE Reprise
Rafi Bistrizer Jung Jung Su Fengcheng WuMing Xie Pawel Potasz
University of Texas at Austin
Intrinsic Spin Hall Effect
Murakami, Nagaosa, and SCZ Science (2003)Sinova et al. PRL (2004)
Bilayer Two-Dimensional Electron Systems
< "#$ "% > ≠ 0
Spatially IndirectExciton Condensate
PRB (1994,95,96)
Electrons and Holes in the QH Regime
Add magnetic field
Particle-hole transformation
Assemble Bilayer
4
Kinetic EnergyQuenching !
!" + !$ = 1
Bilayer Two-Dimensional Electron Systems
Merons !
Charge e/2
Exciton Superflow – in pictures
Drag Counterflow
Su & AHM Nature Phys. (2008)Eisenstein von Klitzing
TL
BL BR
TRe e
e
e
h
Sublattice-Pseudospins
A
B
2D Massless Dirac Equation
vD ~ 106 m/s
2D wavevectorSublatticepseudospin
Bilayer AB stacking
A1 B1
A2 B2
Novoselov et al. – Nature Phys. (2006)
McCann & Falko – PRL (2006)
Bilayer Graphene N=0 FQHE
J.I.A. Li et al. Science (2017)
Fengcheng Wu et al. PRB (2014)
SO(5) Symmetry in Quantum Hall Effect
! = #°
%&
%'
Twisted vdW Heterojunctions
Periodic Tunneling Hamiltonian
TAB(r) AA
BA
AB
Rafi Bistritzer & AHM, PNAS (2011)
Fourier X-form of π-bandinterlayer hopping amplitude
tq decreases very rapidly with q
�1 parameter model
Magic Angles !
Bistritzer & AHM PNAS (2011) Morrell et al. PRB (2010)
43210-2-4
Magic Angle Flat Bands
Insulator Superconductor
-3 -1
T
Ong State
Gaps without Breaking C2T symmetry!Ong State ! = 0
Magic Angle Phase Diagram TAA/TAB=0.8
Continuum Model and Moiré Bands
φ = 2π/3
Rafi Bistritzer & AHM, PNAS (2011)
MATBG Mass Operator
("#, "%, "&)= "(1 + 2+, 1 − +, 1 − +)
+
.
Fock self-energy from remote valence bands
Sensitive Band Topology
Broken Flavor SymmetriesK↑ valence band empty " = −% (non-Ong State)
Xie & AHM arXiv:1812.04213
Insulators at All Quarters – Some Chern
Efetov Group – ICFO (Barcelona)
0 2 4 6 8-10
0
10
20
30
40
E [m
eV]
Nxky+kx
Finite-Size Exact Diagonalization
QP Bands
IncludingRemote-BandSelf-Energy
Ferromagnetic Insulators
Electrons
Holes
Band Shuffling
SCZ Memorial Workshop
Magic Angle TBG: FQHE Reprise
Rafi Bistrizer Fengcheng WuMing Xie Pawel Potasz
University of Texas at Austin