Physical Review Letters,
Год журнала:
2024,
Номер
133(13)
Опубликована: Сен. 26, 2024
Moiré
superlattices
based
on
two-dimensional
transition
metal
dichalcogenides
(TMDs)
have
emerged
as
a
highly
versatile
and
fruitful
platform
for
exploring
correlated
topological
electronic
phases.
One
of
the
most
remarkable
examples
is
recently
discovered
fractional
quantum
anomalous
Hall
effect
(FQAHE)
under
zero
magnetic
field.
Here,
we
propose
minimal
structure
that
hosts
long-lived
excitons-a
ubiquitous
bosonic
excitation
in
TMD
semiconductors-with
narrow
bands.
The
nontrivial
exciton
topology
originates
from
hybridization
moiré
interlayer
excitons
tunable
by
controlling
twist
angle
electric
At
small
angle,
lowest
bands
are
isolated
higher
energy
provide
solid-state
realization
Kane-Mele
model
with
flatbands,
which
could
potentially
support
version
FQAHE.
Science,
Год журнала:
2024,
Номер
384(6696), С. 647 - 651
Опубликована: Май 9, 2024
The
quantum
anomalous
Hall
effect
(QAHE)
is
a
robust
topological
phenomenon
that
features
quantized
resistance
at
zero
magnetic
field.
We
report
the
QAHE
in
rhombohedral
pentalayer
graphene-monolayer
tungsten
disulfide
(WS
Physical Review Letters,
Год журнала:
2024,
Номер
133(20)
Опубликована: Ноя. 12, 2024
Recent
experiments
on
rhombohedral
pentalayer
graphene
with
a
substrate-induced
moiré
potential
have
identified
both
Chern
insulators
and
fractional
quantum
Hall
states
at
zero
magnetic
field.
Surprisingly,
these
are
observed
in
strong
displacement
fields
where
the
effects
of
lattice
weak,
seem
to
be
readily
accessed
without
fine-tuning.
To
address
experimental
puzzles,
we
study
model
interacting
electrons
this
geometry.
Within
self-consistent
Hartree-Fock
(SCHF)
calculations,
find
an
isolated
band
small
bandwidth
good
Exact
diagonalization
density-matrix
renormalization
group
calculations
confirm
hosts
Remarkably,
is
stable
wide
range
angles,
four
through
six
layers,
varying
hopping
parameters,
and-most
strikingly-survives
SCHF
when
vanishes.
In
limit,
state
spontaneously
breaks
time-reversal
translation
symmetry
simultaneously,
giving
topological
crystalline
that
term
"anomalous
crystal."
We
argue
general
mechanism
create
bands
multilayer
graphene,
opening
door
studying
interplay
between
electronic
topology,
fractionalization,
spontaneous
breaking.
Nature Communications,
Год журнала:
2024,
Номер
15(1)
Опубликована: Май 18, 2024
Abstract
Motivated
by
recent
experimental
observations
of
opposite
Chern
numbers
in
R-type
twisted
MoTe
2
and
WSe
homobilayers,
we
perform
large-scale
density-functional-theory
calculations
with
machine
learning
force
fields
to
investigate
moiré
band
topology
across
a
range
twist
angles
both
materials.
We
find
that
the
frontier
bands
change
sign
as
function
angle,
this
is
driven
competition
between
ferroelectricity
piezoelectricity.
Our
calculations,
enabled
methods,
reveal
crucial
insights
into
interactions
different
scales
bilayer
systems.
The
interplay
atomic-level
relaxation
effects
moiré-scale
electrostatic
potential
variation
opens
new
avenues
for
design
intertwined
topological
correlated
states,
including
possibility
mimicking
higher
Landau
level
physics
absence
magnetic
field.
Physical Review Letters,
Год журнала:
2024,
Номер
133(20)
Опубликована: Ноя. 12, 2024
The
standard
theoretical
framework
for
fractional
quantum
anomalous
Hall
(FQAH)
effect
assumes
an
isolated
flat
Chern
band
in
the
single
particle
level.
In
this
Letter,
we
challenge
paradigm
FQAH
recently
observed
pentalayer
rhombohedrally
stacked
graphene
aligned
with
hexagonal
boron
nitride.
We
show
that
external
moiré
superlattice
potential
is
simply
a
perturbation
model
continuous
translation
symmetry.
Through
Hartree-Fock
calculations,
find
interaction
opens
sizable
remote-band
gap,
resulting
narrow
C=1
at
filling
ν=1.
From
exact
diagonalization
identify
phases
various
fillings.
However,
states
also
exist
calculations
without
any
potential.
suggest
(QAH)
insulator
ν=1
should
be
viewed
as
interaction-driven
topological
Wigner
crystal
QAH
effect,
which
subsequently
pinned
by
small
robust
period
around
10
nm
4-layer,
5-layer,
6-layer,
and
7-layer
systems.
Our
work
suggests
new
direction
to
explore
interplay
between
topology
spontaneous
formation
vanishing
limit.
propose
system
generate
control
both
honeycomb
triangular
potentials
through
Coulomb
from
another
layer,
can
stabilize
or
suppress
depending
on
density
of
layer.
