In underdoped cuprates, the interplay of the pseudogap, superconductivity, and charge and spin ordering can give rise to exotic quantum states, including the pair density wave (PDW), in which the ...superconducting (SC) order parameter is oscillatory in space. However, the evidence for a PDW state remains inconclusive and its broader relevance to cuprate physics is an open question. To test the interlayer frustration, the crucial component of the PDW picture, we perform transport measurements on charge- and spin-stripe-ordered La
Eu
Sr
CuO
and La
Nd
Sr
CuO
in perpendicular magnetic fields (H
), and also with an additional field applied parallel to CuO
layers (H
). We detect several phenomena predicted to arise from the existence of a PDW, including an enhancement of interlayer SC phase coherence with increasing H
. These data also provide much-needed transport signatures of the PDW in the regime where superconductivity is destroyed by quantum phase fluctuations.
We synthesize and study single crystals of a new double-perovskite Sr2YIrO6. Despite two strongly unfavorable conditions for magnetic order, namely, pentavalent Ir5+(5d4) ions which are anticipated ...to have Jeff=0 singlet ground states in the strong spin-orbit coupling (SOC) limit and geometric frustration in a face-centered cubic structure formed by the Ir5+ ions, we observe this iridate to undergo a novel magnetic transition at temperatures below 1.3 K. We provide compelling experimental and theoretical evidence that the origin of magnetism is in an unusual interplay between strong noncubic crystal fields, local exchange interactions, and "intermediate-strength" SOC. Sr2YIrO6 provides a rare example of the failed dominance of SOC in the iridates.
Abstract
The origin of the weak insulating behavior of the resistivity, i.e.
$${\rho }_{xx}\propto {\mathrm{ln}}\,(1/T)$$
ρ
x
x
∝
ln
(
1
/
T
)
, revealed when magnetic fields (
H
) suppress ...superconductivity in underdoped cuprates has been a longtime mystery. Surprisingly, the high-field behavior of the resistivity observed recently in charge- and spin-stripe-ordered La-214 cuprates suggests a metallic, as opposed to insulating, high-field normal state. Here we report the vanishing of the Hall coefficient in this field-revealed normal state for all
$$T\ <\ (2-6){T}_{{\rm{c}}}^{0}$$
T
<
(
2
−
6
)
T
c
0
, where
$${T}_{{\rm{c}}}^{0}$$
T
c
0
is the zero-field superconducting transition temperature. Our measurements demonstrate that this is a robust fundamental property of the normal state of cuprates with intertwined orders, exhibited in the previously unexplored regime of
T
and
H
. The behavior of the high-field Hall coefficient is fundamentally different from that in other cuprates such as YBa
2
Cu
3
O
6+
x
and YBa
2
Cu
4
O
8
, and may imply an approximate particle-hole symmetry that is unique to stripe-ordered cuprates. Our results highlight the important role of the competing orders in determining the normal state of cuprates.
We report a systematical structural, transport and magnetic study of Ca or Ba doped Sr2IrO4 single crystals. Isoelectronically substituting Ca2+ (up to 15%) or Ba2+ (up to 4%) ion for the Sr2+ ion ...provides no additional charge carriers but effectively changes the lattice parameters in Sr2IrO4. In particular, 15% Ca doping considerably reduces the c-axis and the unit cell by nearly 0.45% and 1.00%, respectively. These significant, anisotropic compressions in the lattice parameters conspicuously cause no change in the Néel temperature which remains at 240 K, but drastically reduces the electrical resistivity by up to five orders of magnitude or even precipitates a sharp insulator-to-metal transition at lower temperatures, i.e. the vanishing insulating state accompanies an unchanged Néel temperature in (Sr1−xAx)2IrO4. This observation brings to light an intriguing difference between chemical pressure and applied pressure, the latter of which does suppress the long-range magnetic order in Sr2IrO4. This difference reveals the importance of the Ir1-O2-Ir1 bond angle and homogenous volume compression in determining the magnetic ground state. All results, along with a comparison drawn with results of Tb and La doped Sr2IrO4, underscore that the magnetic transition plays a nonessential role in the formation of the charge gap in the spin-orbit-tuned iridate.
Background. In children, growth can be used as a measurable parameter of adequate nutrition and dialysis dose. Despite daily administration of recombinant human growth hormone (rhGH), growth ...retardation remains a frequent problem in children on chronic dialysis. Therefore, we performed an observational prospective non-randomized study of children on in-centre daily on line haemodiafiltration (D-OL-HDF) dialysis with the aim of promoting growth. Patients and methods. Mean age at the start of the study was 8 years and 3 months, and all children had been receiving rhGH treatment for >12 months before enrolment. Mean follow-up time on D-OL-HDF was 20.5 ± 8 months (range, 11–39 months). Renal residual function was either <3 mL/min/1.73 m2 or anuric. Vascular access was a fistula (13/15) or a central venous catheter (2/15). Dialysis was delivered daily, six days a week in 3 hourly sessions (18 h/week), in a predilution OL-HDF mode, allowing a high convective volume (18 to 27 L/m2 body surface area per session), Kt/Vurea on line measured at least 1.4 per session. Results. Mean growth velocity increased from 3.8 ± 1.1 cm/year at inclusion to 14.3 ± 3.8 cm/year during the first year of D-OL-HDF, resulting in a change in height standard deviation score (SDS) over the follow-up period from −1.5 ± 0.3 SDS to +0.2 ± 1.1 SDS. Increase in body mass was also noted without impaired control of blood pressure. Time-average deviation for urea (TADurea) was low at 2.5 ± 0.4 as was TADbicarbonate due to the normal pre and post dialysis bicarbonate levels, respectively, 23.6 ± 0.5 mmol/L and 26.6 ± 0.5 mmol/L. The absence of any dietary restrictions permitted a mean protein diet intake (PDI) of 2.5 ± 0.2 g/kg/day (PDI measured from a 3-day diet survey), contrasting with a mean normalized protein nitrogen appearance (nPNA) of 1.53 ± 0.12 g/kg/day (nPNA calculated from urea dialytic kinetic). A low C-reactive protein was noted in 13/15 children, and mean β2 microglobulin was low, 15.3 ± 0.3.3 mg/L. Conclusions. Daily OL-HDF promotes catch-up growth in children despite on chronic dialysis. This catch-up growth if continued, should allow the children to reach their mid-parental target height in the future. It could be speculated that the improved response to rhGH is the result of several combined factors conducting to less malnutrition and to less cachexia.
We report x-ray resonant magnetic scattering and resonant inelastic x-ray scattering studies of epitaxially strained Sr2IrO4 thin films. The films were grown on SrTiO3 and (LaAlO3)0.3(Sr2AlTaO6)0.7 ...substrates, under slight tensile and compressive strains, respectively. Although the films develop a magnetic structure reminiscent of bulk Sr2IrO4, the magnetic correlations are extremely anisotropic, with in-plane correlation lengths significantly longer than the out-of-plane correlation lengths. In addition, the compressive (tensile) strain serves to suppress (enhance) the magnetic ordering temperature TN, while raising (lowering) the energy of the zone-boundary magnon. Quantum chemical calculations show that the tuning of magnetic energy scales can be understood in terms of strain-induced changes in bond lengths.
PDF
