Advanced Functional Materials,
Год журнала:
2024,
Номер
unknown
Опубликована: Сен. 11, 2024
Abstract
After
decades
of
research,
superconductivity
is
finally
found
in
nickel‐based
analogs
superconducting
cuprates,
with
infinite‐layer
(IL)
structure.
These
results
are
so
far
restricted
to
thin
films
the
case
IL‐nickelates.
Therefore,
nature
interface
substrate,
and
how
it
couples
film
properties
still
an
open
question.
Here,
using
scanning
transmission
electron
microscopy
(STEM)‐
energy
loss
spectroscopy
(EELS),
a
novel
p‐type
defined
by
SrO
termination
SrTiO
3
substrate
observed
(SC)
IL‐praseodymium
nickelate
samples.
Its
interfacial
charge
polarity
compared
previously
reported
n‐type
characterized
TiO
2
termination.
In
combination
ab‐initio
calculations,
that
influence
on
electronic
structure
local
does
not
extend
beyond
2–3
unit
cells
into
film.
This
decouples
direct
driving
superconductivity,
indicates
IL‐nickelate
do
have
universal
model.
Insights
spatial
hole‐distribution
SC
samples,
provided
monochromated
EELS
total
reflection‐hard
X‐ray
photoemission
spectroscopy,
suggest
this
particular
distribution
might
be
directly
influencing
superconductivity.
Chinese Physics Letters,
Год журнала:
2023,
Номер
41(1), С. 017401 - 017401
Опубликована: Дек. 14, 2023
The
discovery
of
high-temperature
superconductivity
near
80
K
in
bilayer
nickelate
La
3
Ni
2
O
7
under
high
pressures
has
renewed
the
exploration
superconducting
bulk
materials.
extension
other
nickelates
a
broader
family
is
also
essential.
Here,
we
report
experimental
observation
signature
trilayer
4
10
pressures.
By
using
modified
sol-gel
method
and
post-annealing
treatment
oxygen
pressure,
successfully
obtained
polycrystalline
samples
with
different
transport
behaviors
at
ambient
pressure.
Then
performed
high-pressure
electrical
resistance
measurements
on
these
diamond-anvil-cell
apparatus.
Surprisingly,
possible
transition
maximum
temperature
(
T
c
)
about
20
observed,
as
evidenced
by
clear
drop
suppression
drops
magnetic
fields.
Although
sample-dependent
relatively
small,
it
appears
all
our
measured
samples.
We
argue
that
observed
signal
most
likely
to
originate
from
main
phase
.
Our
findings
will
motivate
shed
light
understanding
underlying
mechanisms
high-
nickelates.
Communications Materials,
Год журнала:
2024,
Номер
5(1)
Опубликована: Март 13, 2024
Abstract
Recent
progress
on
the
signatures
of
pressure-induced
high-temperature
superconductivity
in
Ruddlesden–Popper
(RP)
nickelates
(La
n
+1
Ni
O
3
)
has
attracted
growing
interest
both
theoretical
calculations
and
experimental
efforts.
The
fabrication
high-quality
single-crystalline
RP
nickelate
thin
films
is
critical
for
possible
reducing
superconducting
transition
pressure
advancing
applications
microelectronics
future.
In
this
study,
we
report
observations
an
active
phase
induced
by
misfit
strain.
We
found
that
favor
perovskite
structure
(
=
∞)
under
tensile
strains,
while
compressive
strains
stabilize
La
2
7
2)
phase.
selection
distinct
phases
governed
strain
dependent
formation
energy
electronic
configuration.
compressively
strained
,
experimentally
determined
e
g
splitting
~0.2
eV
electrons
prefer
to
occupy
in-plane
orbitals.
First-principles
unveil
a
robust
coupling
between
effects
valence
state
ions
nickelates,
suggesting
dual
driving
force
inevitable
co-existence
nickelates.
Our
work
underscores
sensitivity
epitaxial
strain,
presenting
significant
challenge
fabricating
pure-phase
films.
Therefore,
special
attention
stacking
defects
grain
boundaries
different
essential
when
discussing
Journal of Physics D Applied Physics,
Год журнала:
2024,
Номер
57(19), С. 193001 - 193001
Опубликована: Фев. 2, 2024
Abstract
Molecular
beam
epitaxy
(MBE),
a
workhorse
of
the
semiconductor
industry,
has
progressed
rapidly
in
last
few
decades
development
novel
materials.
Recent
developments
condensed
matter
and
materials
physics
have
seen
rise
many
quantum
that
require
ultra-clean
high-quality
samples
for
fundamental
studies
applications.
Novel
oxide-based
synthesized
using
MBE
advanced
field
In
this
review,
we
discuss
recent
progress
new
techniques
enabled
synthesis
complex
oxides
exhibit
‘quantum’
phenomena,
including
superconductivity
topological
electronic
states.
We
show
how
these
produced
breakthroughs
4d
5d
oxide
films
heterostructures
are
particular
interest
as
These
offer
bright
future
ultra-high
quality
National Science Review,
Год журнала:
2024,
Номер
11(8)
Опубликована: Июнь 4, 2024
ABSTRACT
Superconducting
infinite-layer
(IL)
nickelates
offer
a
new
platform
for
investigating
the
long-standing
problem
of
high-temperature
superconductivity.
Many
models
were
proposed
to
understand
superconducting
mechanism
based
on
calculated
electronic
structure,
and
multiple
Fermi
surfaces
orbitals
involved
create
complications
controversial
conclusions.
Over
past
five
years,
lack
direct
measurements
structure
has
hindered
understanding
nickelate
superconductors.
Here
we
fill
this
gap
by
directly
resolving
structures
parent
compound
LaNiO2
La0.8Ca0.2NiO2
using
angle-resolved
photoemission
spectroscopy.
We
find
that
their
consist
quasi-2D
hole
pocket
3D
electron
at
Brillouin
zone
corner,
whose
volumes
change
upon
Ca
doping.
The
surface
topology
band
dispersion
closely
resemble
those
observed
in
hole-doped
cuprates.
However,
cuprate-like
exhibits
significantly
higher
doping
compared
cuprates,
highlighting
disparities
states
phase.
Our
observations
highlight
novel
aspects
IL
nickelates,
pave
way
toward
microscopic
family
its
We
present
an
integrated
procedure
for
the
synthesis
of
infinite-layer
nickelates
using
molecular-beam
epitaxy
with
gas-phase
reduction
by
atomic
hydrogen.
first
discuss
challenges
in
growth
and
characterization
perovskite
NdNiO3/SrTiO3,
arising
from
post
crack
formation
stoichiometric
films.
then
detail
a
fully
reducing
NdNiO3
films
to
phase,
NdNiO2,
hydrogen;
resulting
display
excellent
structural
quality,
smooth
surfaces,
lower
residual
resistivities
than
reduced
other
methods.
utilize
situ
nature
this
technique
investigate
role
that
SrTiO3
capping
layers
play
process,
illustrating
their
importance
preventing
secondary
phases
at
exposed
nickelate
surface.
A
comparative
bulk-
surface-sensitive
study
indicates
polycrystalline
crust
on
film
surface
serves
limit
process.
Abstract
Infinite
layer
(IL)
nickelates
provide
a
new
route
beyond
copper
oxides
to
address
outstanding
questions
in
the
field
of
unconventional
superconductivity.
However,
their
synthesis
poses
considerable
challenges,
largely
hindering
experimental
research
on
this
class
oxide
superconductors.
That
is
achieved
two‐step
process
that
yields
most
thermodynamically
stable
perovskite
phase
first,
then
IL
by
topotactic
reduction,
quality
starting
playing
crucial
role.
Here,
reliable
superconducting
nickelate
films
reported
after
successive
topochemical
reductions
parent
with
nearly
optimal
stoichiometry.
Careful
analysis
transport
properties
incompletely
reduced
reveals
an
improvement
strange
metal
behavior
normal
state
resistivity
over
subsequent
reductions,
offering
insight
into
reduction
process.
Advanced Materials,
Год журнала:
2025,
Номер
unknown
Опубликована: Март 10, 2025
Several
reports
about
infinite-layer
nickelate
thin
films
suggest
that
the
superconducting
critical
temperature
versus
chemical
doping
phase
diagram
has
a
dome-like
shape,
similar
to
cuprates.
Here,
highly
reproducible
state
in
undoped
PrNiO2
grown
on
SrTiO3
are
demonstrated.
Scanning
transmission
electron
microscopy
measurements
show
coherent
with
no
visible
stacking-fault
defects,
an
overall
high
structural
quality
where
possible
unintentional
or
interstitial
oxygen,
if
present,
sum
well
below
measurable
threshold
of
technique.
X-ray
absorption
very
sharp
features
at
Ni
L3,2-edges
large
linear
dichroism,
indicating
preferential
hole
occupation
Ni1+-3
dx2-y2${\rm
d}_{x^2-y^2}$
orbitals
square
planar
geometry.
Resonant
inelastic
scattering
reveal
magnon
excitations
200
meV
energy
magnetic
Brillouin
zone
boundary,
resonant
Ni1
+
peak.
The
results
indicate
that,
when
properly
stabilized,
without
doping.
Physical Review Letters,
Год журнала:
2024,
Номер
133(6)
Опубликована: Авг. 8, 2024
Topotactic
reduction
utilizing
metal
hydrides
as
reagents
has
emerged
an
effective
approach
to
achieve
exceptionally
low
oxidization
states
of
ions
and
unconventional
coordination
networks.
This
method
opens
avenues
the
development
entirely
new
functional
materials,
with
one
notable
example
being
infinite-layer
nickelate
superconductors.
However,
effect
on
atomic
reconstruction
electronic
structures-crucial
for
superconductivity-remains
largely
unresolved.
We
designed
two
sets
control
Nd_{0.8}Sr_{0.2}NiO_{2}
thin
films
used
secondary
ion
mass
spectroscopy
highlight
absence
reduction-induced
hydrogen
intercalation.
X-ray
absorption
revealed
a
significant
linear
dichroism
dominant
Ni
3d_{x2-y2}
orbitals
superconducting
samples,
indicating
single-band
nature
nickelates.
Consistent
T_{c},
3d
asymmetry
manifests
domelike
dependence
duration.
Our
results
unveil
critical
role
in
modulating
Ni-3d
orbital
polarization
its
impact
properties.
ACS Nano,
Год журнала:
2024,
Номер
18(5), С. 4077 - 4088
Опубликована: Янв. 25, 2024
The
metal-hydride-based
"topochemical
reduction"
process
has
produced
several
thermodynamically
unstable
phases
across
various
transition
metal
oxide
series
with
unusual
crystal
structures
and
nontrivial
ground
states.
Here,
by
such
an
oxygen
(de-)intercalation
method
we
synthesis
a
samarium
nickelate
ordered
nickel
valences
associated
tri-component
coordination
configurations.
This
structure,
formula
of
Sm9Ni9O22
as
revealed
four-dimensional
scanning
transmission
electron
microscopy
(4D-STEM),
emerges
from
the
intricate
planes
{303}pc
apical
vacancies.
X-ray
spectroscopy
measurements
ab
initio
calculations
show
coexistence
square
planar,
pyramidal,
octahedral
Ni
sites
mono-,
bi-,
tri-valences.
It
leads
to
intense
orbital
polarization,
charge-ordering,
state
strong
localization
marked
disappearance
ligand–hole
configuration
at
low
temperature.
compound
provides
another
example
previously
inaccessible
materials
enabled
topotactic
transformations
presents
interesting
platform
where
mixed
valence
can
give
rise
exotic
phenomena.
Nature Communications,
Год журнала:
2024,
Номер
15(1)
Опубликована: Июнь 14, 2024
Abstract
The
recent
discovery
of
superconductivity
in
infinite-layer
nickelate
films
has
sparked
significant
interest
and
expanded
the
realm
superconductors,
which
structure
proper
chemical
doping
are
both
essence.
Nonetheless,
reasons
for
absence
bulk
nickelates
remain
puzzling.
Herein,
we
investigate
atomic
defects
electronic
structures
Nd
0.8
Sr
0.2
NiO
2
using
scanning
transmission
electron
microscopy.
Our
observations
reveal
presence
three-dimensional
(3D)
block-like
structural
domains
resulting
from
intersecting
defect
structures,
disrupting
continuity
within
crystal
grains,
could
be
a
crucial
factor
giving
rise
to
insulating
character
inhibiting
emergence
superconductivity.
Moreover,
structure,
without
complete
topotactic
reduction,
retains
interstitial
oxygen
atoms
on
plane
nickelates,
possibly
further
aggravating
local
distortions
planes
hindering
These
findings
shed
light
existence
provide
valuable
insights
into
influence
reduction
orders