Physical Review Research,
Год журнала:
2025,
Номер
7(2)
Опубликована: Май 30, 2025
High-pressure
studies
reveal
a
stark
contrast
between
the
superconducting
properties
of
double-layer
Ruddlesden-Popper
(RP)
nickelates
La2PrNi2O7
and
La3Ni2O7.
While
La2PrNi2O7
exhibits
bulk
superconductivity,
La3Ni2O7
displays
filamentary
behavior,
suggesting
that
superconductivity
is
confined
to
phase
interfaces
rather
than
bulk.
Since
magnetism
emerges
near
phase,
understanding
its
differences
in
La3Ni2O7La2PrNi2O7
essential
for
clarifying
their
underlying
electronic
magnetic
properties.
In
this
work
we
study
responce
La2PrNi2O6.96
under
pressures
up
2.3
GPa
using
muon-spin
rotation/relaxation
(μSR)
technique.
The
application
external
pressure
increases
Néel
temperature
TN
from
approximately
161
K
at
ambient
(p=0)
about
170
p=2.30GPa.
dependence
internal
field
Bint(T)
(i.e.,
order
parameter)
follows
power-law
relation
Bint=Bint(0)(1−[T/TN]α)β,
with
consistent
exponent
values
α≃1.95β≃0.35
across
different
pressures.
value
ordered
moments
Ni
sites,
which
proportional
Bint,
remain
unaffected
by
pressure.
Our
findings
suggest
RP
nickelate
La3Ni2O7
are
broadly
Pr
La
substitution.
slightly
elevated
La2PrNi2O7
compared
La3Ni2O7
represents
most
notable
distinction,
subtle
effects
arising
substitution
within
studied
range.
Published
American
Physical
Society
2025
Physical Review Letters,
Год журнала:
2025,
Номер
134(12)
Опубликована: Март 25, 2025
Recent
studies
of
La_{3}Ni_{2}O_{7}
have
identified
a
bilayer
(2222)
structure
and
an
unexpected
alternating
monolayer-trilayer
(1313)
structure,
both
which
feature
signatures
superconductivity
near
80
K
under
high
pressures.
Using
angle-resolved
photoemission
spectroscopy,
we
measure
the
electronic
1313
samples.
In
contrast
to
previously
studied
2222
find
that
hosts
flat
band
with
markedly
different
binding
energy,
as
well
additional
electron
pocket
splittings.
By
comparison
local-density
approximation
calculations,
renormalizations
Ni-d_{z^{2}}
Ni-d_{x^{2}-y^{2}}
derived
bands
be
about
5
7
4,
respectively,
suggesting
strong
correlation
effects.
These
results
reveal
important
differences
in
brought
by
distinct
structural
motifs
same
stoichiometry.
Such
may
relevant
putative
temperature
superconductivity.
Physical Review Letters,
Год журнала:
2025,
Номер
134(13)
Опубликована: Март 31, 2025
The
recent
observation
of
high-${T}_{c}$
superconductivity
in
the
bilayer
nickelate
${\mathrm{La}}_{3}{\mathrm{Ni}}_{2}{\mathrm{O}}_{7}$
under
pressure
has
garnered
significant
interest.
While
researches
have
predominantly
focused
on
role
electron-electron
interactions
superconducting
mechanism,
impact
electron-phonon
coupling
(EPC)
remained
elusive
and
unexplored.
In
this
Letter,
we
perform
first-principles
calculations
to
study
phonon
spectrum
within
explore
interplay
between
EPC
electronic
by
employing
functional
renormalization
group
(FRG)
approach.
Our
reveal
that
alone
is
insufficient
trigger
pressure.
We
identify
unique
out-of-plane
in-plane
breathing
modes
which
selectively
couple
with
Ni
${d}_{{z}^{2}}$
${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$
orbitals,
showcasing
an
orbital-selective
EPC.
Within
two-orbital
model,
it
revealed
solely
foster
${s}_{\ifmmode\pm\else\textpm\fi{}}$-wave
pairing
characterized
notable
frustration
band
space,
leading
a
relatively
low
transition
temperature.
Remarkably,
find
can
act
concert
promote
interlayer
orbital,
partially
releasing
thus
elevating
${T}_{c}$.
contrast,
inclusion
only
marginally
affects
superconductivity,
distinct
from
cuprates.
Potential
experimental
implications
are
also
discussed.
The
discovery
of
superconductivity
in
pressurized
bilayer
and
trilayer
nickelates
has
generated
significant
interest.
However,
their
superconducting
properties
are
often
dependent
on
sample
quality
pressure
conditions,
complicating
the
interpretation
underlying
physics.
Finding
new
systems
with
optimized
bulk
is
therefore
important
for
advancing
our
understanding
these
materials.
Unlike
cuprates,
where
compounds
typically
exhibit
highest
transition
temperature
(Tc),
nickelate
La3Ni2O7
thus
far
outperformed
La4Ni3O10
reported
Tc.
Whether
have
achieved
optimal
Tc
remains
unclear,
various
scenarios
suggesting
different
possibilities.
Here,
we
report
Pr4Ni3O10
single
crystals,
achieving
a
maximum
onset
Tc
40.5
K
at
80.1
GPa,
significantly
exceeding
30
observed
La4Ni3O10.
nature
confirmed
by
zero
resistance
strong
diamagnetic
response
below
Tc,
volume
fraction
80%.
These
findings
establish
as
genuine
high-temperature
superconductors,
provide
insights
into
mechanisms
driving
superconductivity,
point
to
promising
route
toward
further
enhancing
nickelates.
Published
American
Physical
Society
2025
Physical review. B./Physical review. B,
Год журнала:
2025,
Номер
111(10)
Опубликована: Март 24, 2025
The
discovery
of
high
critical
temperature
(${T}_{c}$)
superconductivity
in
pressurized
${\mathrm{La}}_{3}{\mathrm{Ni}}_{2}{\mathrm{O}}_{7}$
has
ignited
renewed
excitement
the
search
for
novel
high-${T}_{c}$
superconducting
compounds
with
$3d$
transition
metals.
Compared
to
other
ambient-
pressure
superconductors,
such
as
copper-oxide
and
iron-oxypnictides,
unraveling
mechanisms
pressure-induced
poses
significant
unique
challenges.
A
factor
this
phenomenon
seems
be
related
electronic
configuration
orbitals,
which
may
play
a
fundamental
role
driving
superconductivity.
However,
effects
on
mixed-valence
states
$3d$-orbital
cations
their
influence
emergence
remain
poorly
understood.
Here,
we
use
high-pressure
($P$)
low-temperature
synchrotron
x-ray
absorption
spectroscopy
investigate
mean
valence
(\ensuremath{\nu})
change
Ni
ions
${\mathrm{La}}_{3}{\mathrm{Ni}}_{2}{\mathrm{O}}_{7}$.
Our
results
demonstrate
that
at
low
20
K,
\ensuremath{\nu}
remains
relatively
stable
across
pressures
range
from
1
atm
40
GPa.
Based
analyzing
data,
find
pressure,
ambient-pressure
ordered
phases
disappear
both
structural
phase
occur.
revealed
by
our
is
consistent
determined
diffraction,
offering
information
comprehensive
understanding
