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CATEGORIES:Theoretical Physics Seminars
SUMMARY:Efficient simulation of moire materials using the
density matrix renormalization group - Daniel Park
er\, Harvard University
DTSTART:20210311T160000Z
DTEND:20210311T170000Z
UID:TALK4525AT
URL:/talk/index/4525
DESCRIPTION:I will present infinite density-matrix renormaliza
tion group (DMRG) studies of an interacting contin
uum model of twisted bilayer graphene (tBLG) near
the magic angle. (arXiv:2009.02354\, arxiv:2012.09
885). Because of the long-range Coulomb interactio
n and the large number of orbital degrees of freed
om\, tBLG is difficult to study with standard DMRG
techniques -- even constructing and storing the H
amiltonian already poses a major challenge. These
difficulties are overcome using a newly developed
compression procedure (arXiv:1909.0634) to obtain
a matrix product operator representation of the in
teracting tBLG Hamiltonian which we show is both e
fficient and accurate even when including the spin
\, valley and orbital degrees of freedom. To bench
mark our approach\, I focus first on the spinless\
, single-valley version of the problem where\, at
half-filling\, we find that the ground state is a
nematic semimetal. Remarkably\, we find that the g
round state is essentially a k-space Slater determ
inant\, so that Hartree-Fock and DMRG give virtual
ly identical results for this problem. I then disc
uss the role of strain in bilayer graphene. DMRG s
tudies reveal that adding strain to bilayer graphe
ne drives a phase transition\, which may be respon
sible for inconsistent experimental findings at in
teger fillings. These results show that the effect
s of long-range interactions in magic angle graphe
ne can be efficiently simulated with DMRG\, and op
ens up a new route for numerically studying strong
correlation physics in spinful\, two-valley tBLG
in future work.
LOCATION:https://bham-ac-uk.zoom.us/j/8268225040
CONTACT:Dr Hannah Price
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